4891 4895.output

* GB785298 (A)
Description: GB785298 (A) ? 1957-10-23
Bearing quality testing machine
Description of GB785298 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
PATENT SPECIFICATION
Date of Application and filing Complete Specification: May 13, 1954.
No 14005154.
Application made in United States of America on June 2, 1953.
Complete Specification Published: Oct 23, 1957.
Index at acceptance: -Class 40 ( 1), N( 1 A 3 B: 357 F: 357 J).
International Classif ication:-GO 8 c.
COMPLETE SPECIFICATION
Bearing Quality Testing Machine I, HORACE EDWARD FARMER, a Citizen of
the United States of America, formerly of 167, Moross Road, Grosse
Pointe Farms, Michigan, of 62, West Seven Mile Road, S Detroit,
Michigan, United States of America, do hereby declare the invention,
for which I pray that a patent may be granted to me, and the method by
which it is to be performed, to be particularly described in and by
the following statement:-
This invention relates generally to a machine for testing the

manufacturing accuracy of the rollers and races of thrust bearings.
IS It is an object of my invention to provide a machine which will
test roller thrust bearings for manufacturing inaccuracies to avoid
use of low quality bearings.
Another object of my invention is to provide a machine which will
quickly and accurately test roller thrust bearings for manufacturing
inaccuracies.
In my invention, a roller thrust bearing assembly is supported either
by a fixture, or in a housing in which the bearing is to be used, and
the outer bearing race is held by the support or housing against
rotation while the inner race is rotated on the rollers During
rotation of the inner race, a gradually increasing thrust is applied
axially to the bearing for the purpose of urging the engageable
surfaces of the rollers and ways of the races into mutual contact The
axial thrust increases the torque applied by a rotating member which
drives the inner race, by an amount corresponding to the percentage of
roller and race surfaces in contact Accordingly, the torque is a
function of the accuracy of the bearing parts and may be registered to
indicate to an operator whether or not the bearing is satisfactory It
will be understood, that by test and calculation, it is determined for
any given bearing, an end thrust of calculated foot pounds should
produce a certain related torque in a quality bearingn lPrisi In the
accompanying drawings:
Fig 1 is a front perspective view of my roller bearing testing
machine; Fig 2 is a side view thereof with parts 50 broken away and in
section; Fig 3 is an enlarged fragmentary sectional view of a detail
of the machine; Fig 4 is an enlarged view in section, illustrating a
roller bearing under test; and 55 Fig 5 is a diagrammatic illustration
of my machine and control system therefor.
Referring to the drawings by characters of reference, my bearing
testing apparatus includes a machine having a base 20, a super 60
structure 22 and a column 24 Supported by and extending upwardly from
the base 20 is a jack or anvil 26 to support a housing 28 containing a
bearing 30 to be tested for quality and for use in the housing In the
65 present instance, the housing 28 is a section of a motor vehicle
differential housing and the bearing 30 is to be tested for proper
position in the housing and for bearing quality.
Bearing quality as used here has to do with 7 T percentage of surface
contact between rollers and bearing races under an applied axial
thrust on the bearing That is, an axial thrust is applied to urge a
rotating race against the bearing rollers and if the contact 7 i ing
areas are not sufficient to develop a predetermined torque, the
bearing is considered inferior and rejected.
Above the anvil 26, a pair of oppositely disposed, and horizontally

retractable 80 holders 32 engage in openings in bosses of the housing
28 to hold the same against movement This type of fixture or any of
the other well known holding fixtures may be used to hold the housing
28 against move 85 ment during the test and for quick release of the
housing The mechanism for moving the holders 32 is not shown or
described in detail since such mechanism is well known and forms no
part of the present invention 9 o However, the mechanism comprises
essentially, shafts and gears which may be housed 785,298 in base 20
and may be operated by an air pressure cylinder 34 and lever 35 or by
any other suitable means.
In the column 24 is a vertically movable carrier 36 which carries a
rotatable shaft 38 to the lower end of which is secured a member or
quill 40 The quill 40 has a lower end portion 42 of reduced diameter
to engage in the inner race of the bearing and the reduced portion
provides a downwardly facing shoulder 44 to seat on the upper end of
the bearing inner race, providing a frictional drive connection
therewith (see Fig 4).
The carrier 36 is keyed at 46 to the column 24 to prevent turning of
the carrier, and the shaft 38 is joumalled in the carrier 36 by thrust
bearings (not shown) through which vertical movement of the carrier is
transmitted to the shaft At its upper end, the shaft 38 is splined, as
at 48, to a driven shaft of a pulley 52 which is driven by an electric
motor 54 by means of a belt drive.
The mechanism for moving the quill 40 downwardly into driving relation
with bearing 30 and applying axial thrust thereto comprises, in
general, a cam 56, a cam operating motor 58, and a coil spring 66 The
cam 56 is mounted on the column 24 to rotate about a horizontal axis,
and the spring 66 is mounted on the column between the cam 56 and the
carrier 36 Motor 58 is mounted on top of the machine superstructure 22
and drives the cam 56 through a speed reducing mechanism 62, drive
shaft components 61, 63, and an electrically operated device or
magnetic clutch 64 These devices may be mounted on the top of the
superstructure 22.
The magnetic clutch 64 controls operation of cam 56 by motor 58 by
coupling the shaft components 61, 63 together or by uncoupling said
components Motor 58 preferably runs constantly as the machine is
required to test bearings in accordance with a high production quota
When the magnetic clutch 64 is energised, the motor 58 and cam 56 are
coupled together and when clutch 64 is deenergised the devices are
uncoupled On shaft component 63, between clutch 64 and the cam 56 1
provide a magnetic brake 65 to stop rotation of cam 56 at its starting
position.
The spring 66 is retained between the opposed ends of vertically
movable thrust rods 68, 70 which are guided vertically in a tube 72

that is secured to the column and cam 56 The upper thrust rod 68
carries a laterally extending follower 74 which rides on the cam
surface of cam 56, and the lower thrust rod 70 is seamed rigidly, as
at 76, to the lower end of the carrier 36 The spring 66 aids the cam
56 in applying a gradually increasing axial thrust on the bearing.
As is well known, manufacturing inaccuracies appear in the casting and
machining of the housing 28 and to compensate for these inaccuracies,
shims (not shown) are placed back of the bearing so that the location
of the bearing will be as accurate as is practical In the present
machine there is mounted on the column 24, a gauge 75 for 70
registering, in response to the downward movement of the quill 40, the
number of shims or shim thicknesses required The gauge 75 may have a
dial preferably calibrated to indicate number of shims A 75 gauge
operating plunger 80 is operated by a lever 82 which is pivoted to and
in an opening 84 in column 24 for operation by the vertically movable
carrier 36 The outer end of lever 82 engages the lower end of gauge 80
plunger 80 and the inner end of the lever engages a downwardly facing
shoulder 86 on the carrier 36 A light spring 88 holds the inner end of
lever 82 in engagement with the carrier shoulder 86 85 With particular
reference to Fig 5, the magnetic clutch 64 and brake 65 are controlled
by a main relay switch 90 which in turn is controlled by an electronic
tube or tetrode switch 92 The tetrode 92 responds 90 to increase in
line current occasioned by increase in torque on the quill driving
motor 54 That is, if a bearing under test is of desired quality, a
predetermined increase in torque on motor 54, due to the axial thrust
95 on the bearing, will result and as a consequence sufficient current
will flow from tetrode 92 to open relay 90 to de-energise the magnetic
clutch 64 and stop cam 56 Conversely, if the bearing under test is
inferior 100 it will not apply the predetermined torque to motor 54
and consequently tetrode will not open the control relay 90.
The quill driving motor 54 is illustrated as a three phase type which
may be con 10 nected to a suitable source of electric power by main
lead wires 100, 102 and 104 A transformer 106 is provided to lower the
potential suitably for control instrument circuits and comprises the
usual primary coil lie 108 and secondary coil 110 Lead wires 112 and
114 connect opposite ends of the transformer primary 108 to the main
lines 100 and 102 respectively Connected to opposite ends of the
transformer secondary 110 are leads 115 16, 118 of a circuit which
includes the magnetic clutch 64.
A relay 120 controls the magnetic clutch 64 and has the usual coil 122
and a movable armature which carries a contact to engage 120 a pair of
fixed contacts 124 to control clutch 64 and a pair of contacts 125 to
control brake 65 Relay 120 is normally open with respect to contacts
124 and normally closed with respect to contacts 125 The relay coil

125 122 is connected to the transformer secondary 110 by leads 126 and
128 in the latter of which there is a push button starter switch 130.
The magnetic clutch 64 and brake 65 are 130 785,298 and 177.
The tetrode 92 includes an anode 166, a cathode 168, a pair of grids
170, 172, and an indirect heater 174 A lead wire 175 connects anode
166 to one end of relay coil 144 70 and the other end of said coil is
connected by a lead wire 176 to one terminal of transformer secondary
177 Lead wires 178, 180 connect the tetrode heater 174 to terminals of
the transformer secondary 179 75 Rectifier tube 154 has the usual pair
of anodes 182 and an indirect heater 184 Lead wires 186, 188
respectively connect the rectifier anodes 182 to opposite terminals of
the transformer secondary 158 Lead wires 190 80 192 connect the heater
184 to opposite terminals of the transformer secondary 160.
Similarly, rectifier tube 156 includes the usual pair of anodes 194,
and an indirect heater 196 Anodes 194 are connected to 85 opposite
terminals of the transformer secondary 161, and heater 196 is
connected to opposite terminals of the transformer secondary coil 197
by leads 199.
The transformer 162 has a primary coil 90 which has one terminal
connected by a lead wire 202 to motor 54 and has an opposite terminal
connected to main lead wire A resistance 204 is connected to lead 202
and to the primary of transformer 164 95 such that the resistance and
coil are in parallel circuit with motor 54.
Connecting the tetrode grid 170 and one terminal of the transformer
secondary 177, is a lead 206 which connects to the cathode 100 168 A
lead 208 connects a terminal of transformer secondary 161 to lead 206,
and in lead 206 is a condenser 210 in circuit with which there is a
parallel resistance 212 Connected to the resistance 212 and to lead
208 105 is a potentiometer 214 From the adjustable contact of
potentiometer 214, a lead 216 connects to heater 184, and in parallel
lead 216 is a condenser 218 and a resistance 220 which connect to the
tetrode grid 172 by a 110 lead 222 in which there is a resistance 224.
In lead 175, I provide a meter 226 for registering or indicating to
the machine operator the quality of the bearing under test When
tetrode 92 conducts, the meter 115 226 registers whether or not the
predetermined torque for quality bearings is reached by the bearing
under test Also a signal lamp 228 in lead 175 may be provided to
register when the bearing under test develops 120 the established
torque which will cause tetrode 92 to conduct sufficiently to operate
relay 90 Relay 90 may be of the delayed action type on closing so as
to allow the operator sufficient time to read the meter 125 226 The
lamp 228 is provided to signal the machine operator when he should
read the shim gage 75 It is to be understood that the meter 226
registers when the tetrode begins to conduct and continues to register

as the 130 operated by direct current supplied by a bridge type
rectifier 132 which has alternating current terminals A and B, and
direct current terminals C and D Leads 116 and 188 respectively
connect the rectifier terminals A and B to opposite ends of the
transformer secondary 110 A lead 134 connects the direct current
rectifier terminal C to one of the relay contacts 124, and a lead 136
-0 connects the other contact 124 to one end of the magnetic coil of
clutch 64 The other end of the magnetic coil is connected by a lead
138 to the direct current terminal D of the rectifier 132, thus
completing the connections from rectifier terminal C through relay
contacts 124 and the clutch coil to the other rectifier terminal D
Similarly, a lead 137 connects the direct current terminal C of the
rectifier 132 to one of the relay contacts 125, and a lead 139
connects the other contact 125 to the magnetic coil of brake 65, the
other end of said coil being connected through lead 138 to the
rectifier terminal D.
Relay 120 controls a second pair of contacts 140 of a holding circuit
for maintaining coil 122 energised after release of push button switch
130 Relay 90 controls the holding circuit of relay coil 122 and thus
is the principal control of the magnetic clutch 64 A limit switch 131
is used to stop cam 56 at its starting position when quill 40 is in
its up or raised position.
The relay 90 includes the usual movable armature contact 142, coil
144, and a pair of fixed contacts 146 A lead 148 connects -one of the
fixed contacts 146 to one of the holding relay contacts 140 and the
other of the contacts 146 is connected by a lead 150 to lead 128
between the pushf button switch 130 and the relay coil 122 The other
of the contacts 140 of relay 120 is connected by a lead 152 to lead
118 and thus to the transformer secondary 110 Upon pressing the push
button switch 130 and pulling up of relay 122, the following holding
circuit is completed to relay coil 122: From one end of the
transformer secondary 110, through lead 118, lead 152, contacts 140,
lead 148 normally closed contacts 146, lead 150, relay so cold 122 and
through lead 126 to the other end of the transformer secondary 110
Thus, it will be seen that when push button switch is pressed, the
relay 122 energises a circuit to the magnetic clutch 64; the circuit
of SS the brake 65 is broken, closes a holding circuit for relay 122
and that the holding circuit is under control of relay 90.
The electronic device includes the tetrode 92, a rectifier tube 154,
and a second rectio fier tube 156 The rectifier tubes 154, 156 receive
alternating current respectively from secondary coils 158, 161 of a
pair of transformers 162, 164, and supply direct current to the
tetrode 92 The transformer 164 has the additional secondary coils 160,
179, 197 785,298 torque is gradually increased on the motor 58 The

meter 226 is a convenience for the operator to inform him whether or
not a bearing passes the test.
Main leads 102 and 104 are directly connected to motor 54, but main
lead 100 is connected in circuit such that current flowing
therethrough flows through the parallel combination of resistance 204
and transformer primary coil 200 and then to motor 54 Thus, if the
current requirement to the motor 54 increases, there will be a
corresponding increase in the voltage applied to the transformer
primary coil 200 This voltage is stepped up and applied to the plates
of rectifier tube 154 which produces a pulsating direct voltage which
is filtered to a steady direct voltage by condenser 218, thereby
producing a steady direct voltage across resistance 220 Since the
voltage across resistance 220 is a function of the current flowing to
motor 54 through lead 100, any change in current requirement to motor
54 will effect a corresponding change in voltage developed across
resistance 220.
The positive end of resistance 220 is connected to the control grid
172 of tetrode 92, and the positive end of resistance 212 is connected
by lead 206 to the cathode 168 Also, resistance 220 has its negative
end connected by lead 216 to the adjustment arm of potentiometer 214
The resistance of potentiometer 214 is connected across a portion of
resistance 212 at the negative end thereof so that by varying the
position of the potentiometer arm, the potential difference between
the positive end of resistance 212 and resistance 220 can be varied
and hence the potential difference between the cathode and the control
grid of the tetrode 92 can be varied.
The anode 166 of the tetrode 92 receives its power through relay coil
144 from the transformer secondary coil 177 When the control grid of
the tetrode 92 is made slightly negative with respect to its cathode
168, the tetrode 92 will not conduct, and relay coil 144 will remain
de-energised However, when the control grid of the tetrode 92 is at
zero potential or slightly positive with respect to its cathode, the
tetrode 92 will conduct and if the potential is sufficient, relay coil
144 of relay 90 will be energised.
By means of the potentiometer 214, the motor load at which tetrode 92
will conduct sufficiently to energise relay coil 144 of relay may be
selected If the load on motor 54 increases, as a bearing is being
tested, to the value for which the potentiometer 214 is set the
tetrode 92 then causes relay 90 to be energised to stop rotation of
the cam 56.
Also meter 226 will register the bearing as satisfactory and the
signal lamp will also be lighted to signal the operator to read the
meter and shim gage As previously mentioned the closing action of
relay 90 is delayed to give the operator an opportunity to observe the

meter 226 and read the shim gage 76.
When the machine operator pushes button switch 130 the coil of relay
120 is ener 70 gised and closes contacts 124, the circuit holding
contacts 140 are closed and opens the brake contacts 125 of magnetic
brake As a result of the closing of contacts 124, the clutch 64 is
energised to couple the 75 motor 58 to the cam 56 which is then
rotated and moves carrier 36 and rotating quill 40 downwardly toward
the bearing under test.
The lower reduced end 42 of the quill 40 engages in the inner race of
the bearing and 80 the quill shoulder 44 engages with the upper end of
the race, thus frictionally engaging and rotating the inner race on
the roller bearings Through the spring 66, the cam 56 exerts a
gradually increasing axial thrust 85 against the bearing, and if the
thrust applies a predetermined torque on the motor 54, the tetrode 92
responds by energising relay 90 which de-energises clutch 64 to stop
the cam 56 The signal light 228 is energised when 90 the said
predetermined torque is reached to signal the operator to read the
shim gage 75 and the torque meter 226 When relay 90 opens the contacts
146, the holding circuit of relay 120 is broken and so to re-start cam
95 56 to return the cam to its starting position it is necessary for
the operator to press the starter button 130 The cam will be stopped
in its starting position by limit switch 131.
Rotation of the cam is interrupted to give 100 the operator time to
observe the torque meter and shim gauge If the bearing does not pass
the test, the cam 56 will make an uninterrupted rotation to its
starting position, where it will be stopped by limit switch 105 31
When the cam 56 is stopped, either by tetrode 92 or limit switch 31,
relay 120 is de-energised This de-energises the clutch 64 and
energises the brake 65.
It should be understood that while the 11 C cam has a high point at
which maximum thrust is applied on the bearing under test.
this should not be taken to mean that the bearing tested must develop
a predetermined torque on the motor 58 at the maximum 115 thrust or at
any predetermined thrust, in order to be classified as a high quality
bearing To clarify this point the following specific example is given:
For a given type of bearing to be tested, a norm or standard 12 C,
must be established by which to measure the quality of the bearings
The bearing of the present disclosure is for use in holding the pinion
gear of a motor car drive shaft in proper meshed relation with the
differential 125 ring gear For this bearing I have established by
calculation and test that the axial thrust applied to the bearing
should start at about 1,600 pounds and be increased by the cam to
about 2200 pounds and that within 130 785,298 785,298 5 these limits,
the bearing should apply a torque of about 12 5 inch pounds on the

quill 40 for the bearing to be classified as a quality bearing.
Thus, an unsually well made bearing may register the required 12 5
inch pounds of torque at say 1,800 pounds of thrust and another
acceptable bearing may register the 12.5 inch pounds of torque at
2,000 pounds of thrust However, should the maximum of 2,200 pounds of
thrust be applied to a bearing without registering the required
torque, the bearing is rejected as inferior.
From the above it will be seen that the proper torque for a given
bearing is predetermined and that the applied thrust that will
register the predetermined torque may vary within established limits.
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* 5.8.23.4; 93p
* GB785299 (A)
Description: GB785299 (A) ? 1957-10-23
Isolation of coloring compounds from caramelized sugars
Inventors: JAMES EDWIN CLELAND and ALVIN LEROY MEYER 785,299 Date of
Application and filing Complete Specification: May 17, 1954.
No 14433/54.
Complete Specification Published: Oct 23, 1957.
Index at acceptance:-Classes 49, B 5; and 127, F.
International Classification:-A 23 g, I.
Isolation of Coloring Compounds from Caramelizedl Sugars We, UNION
STARCH AND REFINING COMPANY, a corporation of the State of Indiana,
United States of America, of Columbus, Indiana, United States of
America, do hereby declare the invention, for which we pray that a

patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement: This invention relates to a process and apparatus for the
isolation of the coloring compounds from caramelized sugars.
In general the process disclosed takes advantage of the fact that
commercial caramel color owes its coloring power to the colloidal
phase of the mixture of compounds present.
The usual acid-proof types, for instance, widely used in carbonated
beverages, ordinarily consist of about 70 % solids and 30 % of water
Of the total solids present only about % are color bodies or compounds
having high tinctorial power and the remainder of the solids, with the
exception of minor quantities of ash, are sugars or intermediate
products modified to a greater or less extent by the burning procedure
or other processing applied.
The approximately 25 % of the solids that provide the coloring power
of commercial caramel color are in the colloidal state and dispersed
in a medium of sugar syrup It constitutes a very stable lyophilic or
hydrophilic colloidal system and most of the tests devised to evaluate
caramel colors have the objective of comparing this stability under
unfavorable conditions Hence the various acid boiling, tannin,
alcohol, and compatibility tests.
One aspect of this invention is based on the discovery that the
properties of caramel color bodies can be interpreted in terms of
colloidal chemistry Thus these color bodies are lyophilic or
hydrophilic colloids with definite isoelectric points, are denaturable
(reversibly or irreversibly), and a precipitatable, as will more fully
be explained below.
In general there are three important types lpricr of caramel color on
the market today and they are best differentiated by consideration of
some of their colloidal characteristics as follows:
1 The most important variety in terms of volume produced, is the
so-called " AcidProof " type, very widely used in carbonated beverages
It has relatively weak electrical properties but is of a very definite
and consistent character The isoelectric point is in the very low
range and may be around 0 3; at any rate it is below 3 2 As the p H is
raised above this the colloidal system exhibits increasingly
electronegative characteristics up to about p H 7 0 Some of these
"Acid-Proof " caramel colors are extremely stable and have phenomenal
resistance to relatively strong acid concentrations before any
denaturation or coagulation becomes evident They are very stable in
the presence of tannins or other negatively charged colloidal
substances as would be predicted from their electronegative character
In addition they are likely to exhibit high resistance to ageing or
colloidal changes induced by time.

2 Another well known commercial type is characterized by a high
isoelectric point at around 7 0 p H This variety exhibits pronounced
electropositive characteristics down to relatively low p H ranges The
variety is not as stable in the acid tests as type No 1 above but is,
of course, much more stable in the presence of electropositive
colloidal substances such as those encountered in beers Hence this
type of caramel color is sometimes known as Brewer's Color Relatively
smaller volumes of this variety are manufactured in the United States
as the major users of caramel color in that country are the carbonated
beverage manufacturers.
3 There is a type of caramel color having electropositive colloidal
characteristics that is manufactured in large quantities and is
sometimes referred to as Baker's & Confectioner's Caramel Color The
isoelectric point is somewhat higher than that of type No 1 and is
likely to fall between 3 0 and 4 0 p H This variety is very stable in
the acid boiling tests but will haze up immediately in the presence of
negative colloidal substances like tannins and eventually throw down a
heavy precipitate.
It can be made satisfactorily in conventional burning processes with
20 to 30 % greater tinctorial power than the " Acid-Proof " or
beverage type described under No 1 It is less resistant to development
of instability with age, however, and in this way resembles type 2
(Brewer's) more than type 1 It is inclined to be much more viscous
than the latter at the same specific gravity.
All of these types have modifications or sub-groups in the form of
specialties but they can be classified under the above general
headings on the basis of colloidal characteristic.
It is obvious that a caramel color having electronegative colloidal
characteristics (such as type 1, " Acid-Proof " or beverage type)
should never be mixed with one having electropositive character such
as types 2 and 3 (" Brewer's " and " Bakers ") They will neutralize
the charges prevailing in each other and a portion of the colloidal
content of each system will become unstable and eventually precipitate
This is why certain types of caramel color are referred to as "
incompatible " We have found that the colloidal systems of caramel
color are generally lyophilic in nature and tend to resemble starch
gels, gelatin and certain proteins in many of the colloidal aspects
The caramel colors have well defined isoelectric points, for instance,
but no great loss of stability is suffered by the colloidal phase when
that point is reached The addition of electrolytes has only a slight
influence on stability.
The most effective means of rendering the colloidal phase unstable and
causing coagulation and precipitation of the color bodies is by the
addition of alcohols and similar hydrophilic liquids as disclosed in

our patent specification No 685,961, for example The reason such
alcohols act to precipitate the color bodies is apparently because
they bring about a dehydration of the colloidal substances and cause
them to coagulate and settle in a well defined layer easily separable
from the sugar syrup Such liquids are hereinafter termed alcoholic
dehydrating agents and consist of those alcohols which are soluble in
water and mixtures of such alcohols, e g methyl, ethyl and the propyl
alcohols Some water may be present with the alcohol or alcoholic
mixture.
After the separation of the colloidal and crystalloidal constituents
has been made, i e.
the color bodies from the sugars, and the alcohol removed from the
color bodies it is found that the colloidal fraction can be repeptized
very readily in water and again produces a very stable system In other
words, it is a reversible system and the sugar syrup dispersing medium
can be replaced with water without impairing the colloidal stability
In this manner the coloring ability or "tinctorial power" of the
separated solids (color bodies) 70 can be built up to -four or more
times that of the original caramel color solids as will be readily
apparent when it is understood that most of the uncaramelized sugar
has been removed from the mixture and virtually pure 75 color
compounds are isolated.
Among the objects of the present invention is to provide an improved
and economical cons tinuous process of producing caramel colors by the
method of alcoholic separation of the 80 colloidal phase followed by
repeptization of this in the form of a stable aqueous solution, or a
readily dispersible dry powder, both of uniquely high tinctorial
power.
Among other objects of this invention is to 85 provide a process and
apparatus for recaramelizing the residual sugar recovered from the
separation steps and to produce additional high quality coloring
compounds from it until all of the sugar is used up in an efficient 90
manner and with maximum yields of color.
Another aspect of this invention is based on the discovery that in
order to effectively reutilize the residual sugar recovered from the
caramel color solution after separation of the 95 color bodies, the
increase in impurities including the ash content of the recovered
product must be kept under control When the impurities (including the
ash) in the sugar reach a certain level the colloidal properties of
the 100 caramel are affected by the impurities or ash in a way which
is quite unpredictable, whereby the acid resistance and similar
properties of the color produced are inferior.
The objects of this invention are attained by 105 separating caramel
color bodies from an acidproof type caramel color syrup, recovering

the uncaramelized sugars and recaramelizing under such conditions that
the impurity and ash content of the sugar does not exceed a certain
110 level After the ash content of the syrup has reached a certain
value which prevents the obtaining of good acid-proof color bodies
therefrom, the ash can be removed as by ionexchange methods or the
syrup can be utilized 115 to produce a different type of caramel color
(the " Brewer's " or " Baker's " type described above, for example).
In the precipitation the bulk of the impurities and the ash content of
the original caramel 120 color syrup remain with the dissolved portion
so that the ash and other impurities are simultaneously built up A
convenient method of measuring the total content of impurities is to
measure the ash content It has been found 125 that it is not possible
to produce satisfactory acid-proof caramel color from the reclaimed
sugar syrup when the ash content is increased to over 11 % (based on
the weight of the sugar present) A considerable portion of the 130
785,299 ash content may be due to the catalysts added during the
caramelizatibn step Another deterrent to the production of good acid
stable color is the presence of over polymerized sugar The nature of
all the reactions which together produce the color bodies is not known
but one reaction is a polymerization of the sugar bodies wherein the
crystalloidal sugar molecules are polymerized to approximately
colloidal dimensions However this polymerization must not be carried
too far and the presence of too many highly polymerized molecules
tends to produce a color of decreased acid stability.
According to a preferred modification of this invention the excessive
build-up of both ash and excessively polymerized molecules in the
reclaimed syrup is prevented by adding fresh make-up sugar to the
reclaimed, the amount of make-up sugar being approximately equal to
the amount of sugar taken out as color and lost during the process The
combined syrup is then caramelized and less catalyst is required thus
preventing the excessive build-up of ash to the catalyst, but even so
it was surprising to find that the reclaimed sugar can be recycled a
much larger number of times and the ash content can be allowed to
increase up to 11 0 % before the acid instability of the color product
becomes apparent One explanation of this phenomenon may be that the
fresh make-up sugar (which is preferably pretreated to polymerize it)
may act to prevent excessive polymerization of the reclaimed sugar.
Whether make-up sugar is added or not it is necessary to concentrate
the reclaimed sugar to a gravity of 44-47 Be before recaramelizing the
product in order to produce the acidproof product of the invention in
the ultimate degree.
TABLE I
Catalysts There are, of course, a great many possible ways of handling
reclaimed or residual sugar in the reburning operation A number of

these are practical to a greater or less degree but we have found that
certain methods of handling or reburning schedules are much more
economical and lend themselves better to a continuous, smoothly
operating process These are the preferred methods disclosed in the
following illustrations but are not to be construed as limiting the
invention except as delineated in the appended claims.
One method of handling the reclaimed sugar is merely to strip the
alcohols from it and concentrate to about 450 Be and reburn by
standard procedure chosen This method has been explored through a
considerable number of cycles and data are tabulated below in Table I
to illustrate results, as follows:
(A) (B) H 2504 NH, (NH 4)2 SO 4 % on 450 Be sugar basis (C) Bisodium
Sulphite Lbs.
37.8 Be caramel produced Lbs Dry substance (D.S) color bodies
separated % Ash dry substance basis (D S B) on caramel 1 Sugar 100 0
33 1 01 0 56 2 43 112 35 20 71 2 70 2 67 72 32 3 0 42 0 65 1 30 77 93
14 28 4 24 3 47 07 30 5 0 34 0 45 0 87 55 13 11 04 4 62 4 32 22 31 5 0
43 0 50 0 93 38 52 8 01 5 70 22 17 29 8 0 41 0 50 0 95 26 06 4 92 6 57
15.57 Caramelization separation cycle Lbs 450 sugar remaining % of
sugar used in cycle 00 to o 785,299 The material started with in this
case was a commercial caramel color of the "AcidProof " or "Beverage "
type The color was separated by dehydration-precipitation of the
colloidal phase with alcohol Then the residual sugar was stripped of
volatiles, concentrated and reburned to produce caramel color by the
same procedure but with catalyst adjusted to quantity used This
operation was repeated five times and it will be observed that the
quantity of sugar available for reburn decreased each time because of
color removal and shrinkage inherent in the operation.
The four lots of color produced were subjected to some of the standard
tests designed to evaluate colloidal stability and the following
results were obtained:
TABLE IA
T.P Finished Colour Minute Acid Boil Test Acid Tannin Test Neutral
Tannin Test 2 26 0 A A A 3 24 0 A A A 4 26 0 A A A 23 0 C A A For
details of tests see Ind & Eng Chem Anal Edn Vol 10, p 349, 1938.
Tinctorial Power.
Tests on each lot were satisfactory up to lot No 5 when a "C" value
(slight precipitation) was obtained in the acid boil test Later runs,
however, demonstrated that satisfactory acid-proof color could be made
in this cycle and succeeding ones by manipulation of the catalysts and
burning procedure The method, however, suffers from three obvious
faults, as follows:
1 The ash and other undesirable impurities tend to accumulate in the
reclaimed sugar and begin to reach an impractical level about the

fifth cycle This can be handled by ion exchange methods but the step
is costly.
2 The quantity of sugar available diminishes each time and would
require variation in the process with each bum or combination with
other residues to make up a full batch.
3 Polymerization may proceed too far with a tendency to instability If
it is desirable to stop reclaiming sugar after the fifth burn with the
objective of reburning to acid-proof color, it is obvious that a
different grade, tolerating a higher ash, can be made and diverted
into other channels if market conditions are flexible enough to handle
The sugar could be diverted to other uses and would not constitute
more than 20 % of the solids originally present in the first bum or
starting quantity of caramel color.
A logical development of this system would be a method of blending
residual sugar from several lots after the first and subsequent
separations and reburning this mixture This system can be set up to
provide a uniform quantity of sugar for each reburn but results in a
complex schedule and requires excessive storage space An acceptable
product can be made in this manner but the system suffers from the
same limitations noted in the first illustration above The build-up in
ash and other impurities is rapid.
It has now been found that the most efficient and satisfactory method
of operation is to replace the solids used in color production and
processing shrinkage with fresh sugar before each reburning step In
this manner the batch size is maintained and the ash accumulation is
held in abeyance for many additional cycles In the preferred
embodiment of this invention the fresh sugar is polymerized before it
is blended with the recovered sugar.
This polymerization may be accomplished by a method of acid reversion
described in our patent specification No 696,736 According to this
patent sugar solutions to be caramelized are first preheated at a p H
of 0 2 to 4 0 to polymerize the sugar.
Different proportions of polymerized fresh sugar and reclaimed sugar
can be employed as shown by the following results:
7 J 785,299 TABLE II
Exp Polymerized Reclaimed Catalyst No sugar sugar A Catalyst Catalyst
B C 1 75 25 0 95 0 73 2 47 275 2 25 75 0 59 0 91 1 82 275 3 50 50 0 73
1 01 2 15 275 Results of standard tests on these burns were as
follows:
Baum 6 5 Minute Acid Neutral T P.
Exp finished Acid Boil Tannin Tannin of No color Test Test Test Prod.
1 37 8 A A A 22 0 2 39 8 A A A 25 0 3 37 3 A A A 27 0 The stability
tests show that a blend oi reclaimed sugar and polymerized fresh sugar
can be satisfactorily caramelized in any proportions to yield a

caramel color of high quality when the reclaimed sugar used is
recovered from the first separation as in the above example This would
not necessarily hold if all the reclaimed sugar used came from a later
burn, for instance the 6th or 7th in a series like that illustrated in
Table I, and constituted a large percentage of the make-up.
In all probability the ash content would be relatively high under such
conditions unless special precautions had been exercised to minimize
it.
It was found, however, that quality could be maintained and a standard
procedure set up if the sugar make-up for each burn-separation step,
after the first, was composed of the reclaimed sugar from the
preceding separation plus enough fresh sugar to replace the color
bodies (colloidal phase) removed, chemical losses and processing
losses In this manner the volume of the batches could be maintained
through all cycles and appreciable deterioration in quality of the
recovered color could be held in abeyance much longer or through a
greater number of recaramelization and separation steps.
Temp.
OF.
S TABLE III
Percent Polymerized Cycle corn No sugar 1 100 2 37 3 3 38 6 4 37 9 32
2 6 37 3 7 33 6 8 27 4 9 35 0 34 2 11 33 1 12 36 7 13 34 6 14 35 2 36
8 16 33 6 Percent Re Sugar Ammonium Bisodium Heating Baum 6 T P.
claimed B 6 i of Ammonia sulfate sulfite Temp finished finished sugar
blend %D S B %D S B %D S B 'F product caramel 0 45 0 116 0 64 2 79 275
37 8 23 0 62.7 45 0 0 62 0 87 1 98 275 37 85 27 5 61.4 45 0 0 72 0 80
2 00 275 38 2 28 0 62.1 45 0 0 75 0 74 1 99 275 38 35 26 0 67.8 45 0 0
71 0 75 1 92 275 38 0 27 0 62.7 45 0 0 75 0 75 1 98 275 37 6 23 5 66.4
45 0 0 72 0 75 1 94 275 38 35 25 5 72.6 45 0 0 68 0 76 1 86 275 38 6
24 5 65.0 45 0 0 70 0 81 1 95 275 37 8 25 0 65.8 45 0 0 69 0 81 1 94
275 37 95 26 0 66.9 45 0 0 69 0 81 1 93 275 37 7 25 5 63.3 45 0 0 71 0
81 1 97 275 38 05 24 0 65.4 45 0 0 70 0 81 1 95 275 37 8 24 5 64.8 45
0 0 70 0 81 1 95 275 37 65 25 5 63.2 45 0 0 71 0 80 1 97 275 37 95 25
5 66.4 45 0 0 69 0 81 1 93 275 38 1 24 5 Pure Min 10 Min Neut Acid
color Acid Acid Tannin Tannin Percent Test Test Test Test Yield A A A
A 25 0 A A A 30 5 A A A 29 7 A A A 24 7 A A A 29 1 A A A A 23 6 A A A
A 23 4 A A A A 25 2 A A A A 26 0 A A A A 26 0 A A A A 26 2 A A A A 25
0 A A A A 25 4 A A A A 26 3 A A A A 26 4 A A A A 25 7 00 o TABLE
III-continued Percent Polymerized Cycle corn No sugar Percent
Reclaimed sugar Sugar Be of blend Ammonium Bisodium Ammonia sulfate
sulfite %D.S B %D S B %D S B. 17 34 7 65 3 45 0 0 70 0 81 18 36 2 63 8
45 0 0 71 0.81 19 34 9 65 1 45 0 0 70 0 81 34 3 65 7 45 0 0 69 0 81 21
36 7 63 3 45 0 0 71 0 80 22 35 3 64 7 45 0 0 70 0 81 1.95 275 1.97 275
1.95 275 1.94 275 1.97 275 1.95 275 38.1 23 5 37.75 25 5 37.95 26 0

37.8 25 0 37.8 25 0 37.95 25 5 A A A A 25 0 A A A A 26 1 A A A A 26 9
A A A A 25 7 A A A A 25 9 A A A A 26 3 23 35 2 64 8 45 0 0 70 0 81 1
95 275 37.85 26 0 A A A A 26 7 24 33 6 66 4 45 0 0 69 0 81 1.93 275
37.8 24 5 A A A A 25 3 In a typical series of runs polymerized corn
sugar of 450 Be, such as prepared by the process set forth in our
patent specification No.
696,736 is the starting material This polymerized corn sugar is
employed as make-up sugar as well as the starting material In the
first run (Table III) 1 16 % of ammonia, 0.64 % of ammonium sulfate
and 2 79 % of bisodium sulfite are added to the sugar as catalysts The
product is heated to 2750 until a tinctorial power of 23 0 (Lovibond
units) is obtained The gravity of the finished product is decreased
during caramelization to approximately 380 Be The color is
precipitated by a mixture of methanol and isopropanol and a % yield is
obtained.
The residual sugar was reclaimed and amounted to approximately 63 % of
the original corn sugar (by weight) so that 37 % of fresh make-up
sugar is added and the blend is concentrated to 450 Be To this
solution 0.62 % of ammonia, 0 87 % of ammonium sulfate and 1 98 % of
bisodium sulfite are added (in addition to the catalysts which are
already present from the reclaimed portion of the blend) The
caramelizing process is repeated as in the original run.
In the same way 22 additional runs were made and in each case the
reclaimed sugar employed was from 60-73 % of the blend and the added
make-up sugar of course varied from 40-27 % of the blend Comparable
additions of catalysts were employed.
In each case the blend was concentrated to 450 Be and the caramelizing
temperature was 275 F The yields of coloring compounds varied from
23-30 % and in each case the color bodies obtained each passed the (
1) 5 minute acid test, ( 2) the 10 minute acid test (with the
exception of runs 2 to 5 where this test was omitted), ( 3) the
neutral tannin test and the acid tannin test with a rating of A.
The residual sugar left after the 24th run may be made into Baker's
and Brewer's color by any known process A very satisfactory Heating
Temp.
OF.
Baum 6 finished product T.P.
finished caramel Min.
Acid Test Min.
Acid Test Neut.
Tannin Test Acid Tannin Test Pure color Percent Yield process
comprises the steps of pretreating the remaining sugar by adding 0 1-5
% of an alkaline reagent and heating to 150-250 F.
for 4 to two hours The syrup is then acidified back to a p H of 2-5

and caramelized at 320-3800 F without adding any additional catalysts.
The accompanying rawing is a flow sheet illustrating successive steps
and the combination of apparatus made according to the invention.
The apparatus may be divided broadly into a precipitating section A
(enclosed in dotted lines); a color purifying section B; a residual
sugar recovery section C; a solvent recovery section D; and a
caramelizing section E.
Boxes 62 and 66 not included in any of these sections are merely
alcohol or precipitant storage tanks.
Caramel color of any commercial grade but preferably of a very stable
variety, and having a Baume of 36-40 flows through line 1 into
measuring tank 2 which measures the exact volume for a batch by
discharging any excess through line 3 Tank 2 is equipped with an
agitator and a coil which can be used to heat or cool the caramel
coloring in order to achieve a desired operating temperature which may
be in the range of 40 to 80 F.
An alcoholic dehydrating agent, which may consist, for instance, of
methanol and isopropyl alcohol in a ratio of approximately 4 to 1 and
sp.gr 0 84 to 0 86, corrected to 80 T, flows from storage through line
4 into measuring tank 5 This tank is equipped with an overflow line 6
so the quantity of alcoholic dehydrating agent can be accurately
controlled The alcoholic dehydrating agent leaves tank 5 through line
7 and enters tank 8.
When the measured quantity of alcoholic dehydrating agent is in tank
8, caramel color is allowed to flow through line 9 into tank 8, i.e,
into the alcoholic dehydrating agent This is a relatively slow
addition through a nozzle that breaks the stream up into fine jets and
may whirl to achieve better mixing About 10 minutes is required for
the addition of all the caramel color on the scale on which this
process was operated Tank 8 is equipped with an agitator and vigorous
mixing is applied during the period of the introduction of the caramel
color and for about one minute thereafter The agitator is then stopped
and the mixture of caramel color and dehydrating or precipitating
agent is allowed to stand quietly for about 15 minutes The colloidal
or disperse phase, i e the color bodies, of the caramel color begin to
coagulate as soon as the agitation is stopped and rapidly settle to
the bottom in a denatured or flocculated condition The line of
demarkation is easily discernible in glass equipment and will be about
one-tenth of the distance from the bottom of a cylindrical or other
vertical walled tank The upper layer is about 90 % of the total volume
and contains most of the uncaramelized and partially caramelized
sugars It is quite fluid and flows easily The lower layer, or about 10
%, of the volume, contains most of the colloidal or disperse phase
(color bodies) and is rela 70 tively very viscous and much darker in

color.
The upper layer is decanted through a tilting pipe arrangement
equipped with an interface indicator and flows out through line 10 75
The tilting pipe arrangement may comprise a pipe loosely mounted
adjacent the top of the tank and having a floating device so that the
entrance end of the pipe is just submerged in the top layer so as to
draw off only the surface 80 layer The interface indicator may be a
transparent section of the pipe Because of the difference in specific
gravity of the two layers, the upper one being 0 98 to 0 99 and the
lower one 1 18 to 1 20, it is possible to make 85 a sharp separation
by decantation With predetermined batch sizes, controlled by the
measuring tanks, the line of demarcation falls near the same place
each time and a valved outlet at that point can be used in place of 90
the tilting pipe arrangement with reasonable success if desired.
After removing the upper layer or about % of the volume, containing
the bulk of the uncaramelized sugars, the lower layer, con 95 taining
most of the color bodies, formerly the disperse phase in the original
color, is dropped into tank 12 through line 11 As the addition of
water is required for the next step or stripping of the alcohol from
the color frac 100 tion it was found expedient to add about 55 parts
of water, by volume, through line 13, in tank 8 as this makes the
transfer into tank 12 easier Water in proportions of 40 to 100 parts
per 100 parts of the composition may 105 be added but 55 parts is very
satisfactory.
The color fraction or bottom layer, diluted with 55 parts of water, is
then passed through line 14 into evaporator 15 where the alcoholic
distillate is removed through line 16 and re 110 covered for use in
the next cycle The addition of water is necessary in order to assure
the complete elimination of the alcohol precipitants which may be
undesirable depending on the alcohols employed in precipitating If 115
water is not added the temperature required to complete the
elimination of the alcohols would permanently denature the colloidal
bodies It should be noted here that the solution of color bodies from
which the alcohol 120 has been stripped will support mold and yeast
growth quite well and precautions should be taken to protect the
solution against this possibility If the fraction is reduced to solids
immediately, by spray drying or other means, 125 there is, of course,
no danger of spoilage if the dry powder is reasonably protected from
atnospheric moisture The high color solids recovered are much less
hygroscopic than the original sugar or the solids recovered by merely
130 785,299 of the volume separated by decantation in tank 8 is drawn
through a line 10 and enters a storage tank 24 This material, referred
to as the mother liquor, and containing almost all of the
uncaramelized sugars is moved though 70 a line 25 to an evaporator 26

The alcohol associated with this fraction is stripped fromthe mother
liquor, the vapors thereof passing from the evaporator 26 through line
27 and entering line 16 which also carries vapors from 75 the
evaporator 15 These combined vapors enter a water cooled condenser 28,
are condensed, and enter a line 29, whence they flow to a holding tank
30 The water cooled condenser 28 is vented through the line 31 to a 80
salt brine condenser 32 which condenses residual vapors and returns
them through a line 33 to the tank 30 The salt brine condenser 32 is
in turn evacuated, at point 34, by a steam jet air ejector 35 This jet
pro 85 duces the vacuum requirements for the entire system of
evaporators.
The residue in evaporator '26 is concentrated until a Baume reading of
43-45 is obtained This recovered residue is essentially 90 sugar and
is used to make more caramel color.
The concentrated sugar solution, free of alcohol, may be drawn through
a line 35 into a tank 36 The concentrated sugar remaining after a
predetermined number of cycles (such 95 as 24, for instance, as in
this illustration of the process) may be drawn through a line 37 into
a tank 38 where it is stored until a sufficient quantity has
accumulated to make it desirable to route it to burners equipped to
100 make a less critical type of caramel color than the one dealt with
in this illustration This residual accumulation purged from the
system, after many cycles, may, for instance, be burned to produce
Baker's & Confectioner's color in 105 which high tinctorial power is
of primary importance but where fluidity, acid stability and shelf
life are secondary It is advisable to hold the sugars in both tanks 36
and 38 at about 1300 F so they may be handled and flow 110 readily
Hence these tanks are equipped with heating coils.
Fresh corn sugar of about 45-460 Baume and 70 to 90 % dextrose
equivalent is drawn from a heated storage tank 39 through a line 115
into a closed reaction kettle 41 where it may be polmerized to a
dextrose equivalent of 40 -to 50 % by heat treatment at a p H of 1.0
to 2 0 or in any manner giving equivalent results Any sugar or mixture
of sugars capable 120 of producing a satisfactory commercial color may
be used at this stage for make-up but we prefer the sugar above
described and treated as disclosed After polymerization to 40-50 %
dextrose equivalent has been completed in the 125 reaction kettle
(steam jacketed), a part of the ammonia catalysts required for
caramelization is added and this stops the polymerization of the sugar
in so far as indicated by lowering of the dextrose equivalent is
concerned Resi 130 drying any variety of commercial caramel color.
If the color bodies are to be stored in liquid form for periods beyond
24 hours it is advisable to add a preservative A practical concentrate
containing as high as 50 % solids can be made by evaporation of the

solution of color bodies dissolved in a liquid such as water or
propylene glycol and this is a useful product as the tinctorial power
is at least double that of any unfractionated caramel color available
in commercial channels If an attempt is made to concentrate the
aqueous solution of color bodies much above 50 % solids the viscosity
rises very rapidly and the product is difficult to handle in liquid
form In concentrations around 45 % solids the aqueous solution is a
very fluid and stable liquid of great coloring power as the colloidal
state of dispersion is readily restored by simply redispersing in
water after the alcoholic denaturing or dehydrating agent is removed
The resulting colloidal system has the same lyophilic or hydrophilic
character as in the original caramel color and electrical properties
are very similar In other words an electronegative colloidal character
in the original caramel color will persist in the recovered, isolated
color bodies when redispersed in water, demonstrating complete
reversibility This is one of the essential scientific phenomena on
which this invention rests and it appears to have been hitherto
overlooked that the colloidal system of caramel color can be made so
as to be reversible No irreparable damage is done to the stability of
the caramel color bodies by the methods of this invention.
Sodium benzoate is a satisfactory preservative for the color bodies
when redispersed in water About 0 1 % was found to give adequate
protection if added when the liquid issued warm from the still.
The evaporator 15 should operate under vacuum of at least 26 " at all
times and continuous evaporation is preferable If practiced on a batch
basis the concentration step should not require more than 2 hours of
boiling at 26 " vacuum (Temp not more than 150 'F) as the disperse
phase (color) is heat sensitive and may be denatured in an
irreversible manner so as to not redisperse satisfactorily.
The product can also be dehydrated by the freezing and thawing
methods.
The redispersed and concentrated color bodies, from which the
denaturing alcoholic mixture has been stripped and recovered, leave
the evaporator 15 through a line 18 and go to a cooler 19 where the
product is cooled to below 100 '1 F The liquid product may be drawn
from the cooler 19 through a line 20 and can be packed in suitable
containers from a line 21 as a liquid product or it can be dried to a
powder in a spray drier 22 and packed as a dry product from an outlet
23.
The upper layer or the approximately 90 % 785,299 785,299 dual
recovered sugar from the tank 36 is then drawn through a line 42 and
flows into the reaction kettle 41 where caramelization of the mixture
is accomplished in a conventional manner The quantities of polymerized
fresh sugar, reclaimed sugar, and catalysts, are regullated according

to the recaramelization conditions desired.
Caramel color produced in the reaction kettle 41 is drawn through a
line 43 into a tank 44 after dilution with water to 36-38 Baumd The
caramel color from the tank 44 flows through a line 45 to a filter 46
where a small quatity of sediment is removed The product is then drawn
through a line 47 to a cooler 48 where it is cooled to 80 'F From the
cooler 48 the product goes through a line 49 to a storage tank 50 from
which it is routed back through the line 1 and recycled through the
separation steps above described and the equipment numbered 1 to 50.
The residual sugar in tank 38, i e, the sugar recovered after many
cycles and which it is desirable to purge from the system to a less
critical use, is drawn through a line 51 to the reaction kettle 41
where a conventional caramelization may be carried out The product is
drawn through a line 52 to a storage tank 53 and is packed from an
outlet 54.
The alcohol-water mixture in tank 30 flows through a line 55 entering
an alcohol recovery rectifier still 56 Alcohol vapors enter a line 57
and are condensed in a water cooled condenser 58 The condensed vapors
flow through a line 59 to a tank 60 which is the holding tank for the
alcoholic mixture used as the denaturing agent in the color-sugar
separation.
Precautions are taken to assure that this alcohol mixture has been
recovered and controlled at the specific gravity best adapted to color
separation (about 0 84 to 0 86 in this illustration of the process)
and it is routed through line 4 from the tank 60 The alcohol recovery
practiced in this process must be very efficient and economical to
assure that economic aspects of the process are favorable.
Losses should be not over 1 % and to achieve this the best modem
stills and rectifiers are required.
The vapors from condenser 58 enter the line 61 and this connects with
the line 31 These vapors are recovered in the salt brine condenser 32.
It is desirable to vent the entire system of tanks which contain
alcohol to the salt brine condenser 32 In this way alcohol losses from
the system will be minimized.
Make-up alcohols are drawn into the system as follows:
( 1) From a methyl alcohol storage tank 62, through a line 63 to a
measuring tank 64 and then through a line 65 to the distillate storage
tank 60.
( 2) From an isopropyl alcohol storage tank 66 through a line 67 and
line 63 to a measur 65 ing tank 68 and then through a line 69 to
distillate storage tank 60.
Aside from the many improved features of the process and procedure it
has the outstanding ability of utilizing all of the sugar for the 70
purpose of making actual color whereas all conventional commercial

processes now practiced for caramelization will utilize not more than
30 % of the sugar and merely leave the balance, not consumed by
chemical and pro 75 cess losses, in the dispersing phase of a
colloidal system where it is useless and troublesome as it contributes
nothing to stability and is so denatured as to have no sweetening
ability but rather a disagreeable flavor associ 80 ated with crude
hydrol This outstanding and novel ability of our process to conserve
raw material should assure adoption of the method on a wide scale The
process can for instance reduce the consumption of sugars used for 85
caramel color by 60 to 75 % and it is obvious that this can be
beneficial to countries having to import sugar for this purpose
running into millions of pounds.
* Sitemap
* Accessibility
* Legal notice
* Terms of use
* 5.8.23.4; 93p
* GB785300 (A)
Description: GB785300 (A) ? 1957-10-23
Improvements in or relating to spring clip devices
PATENT SPECIFICAT 1 ON
Date qf Cfin g Comnplete Specification: Malacy 25, 1956.
Ariplication? Date: May 28, 1954 No 15919154.
C"onmplete Specification Publislied: Oct 23, 1957.
Index at Acceptanceo:-Classes 44, BE 4 A 3; and 52 ( 5), B( 2 A: 5 A 1
5 AX).
International Classification:-Fr 06 b.
COMPLETE SPECIFICATION.
Improvements in or relating to Spring Clip Devices.
I, INEIL ARCHIBALD PRIMROSE, LORD PRIMROSE, a British Subject, of

Dalmeny House, South Queensferry, West Lothian, Scotland, do hereby
declare the invention, S for which I pray that a patent may be granted
to me, and the method by which it is to be performed, to be
particularly described in and by the following statement:-
This invention relates to devices for receiving and/or holding an
article and in particular to devices embodying a spring clip wherein
the clip has arms extending from a base which is pivotally mounted on
and secured to a supporting member to enable the article to be turned
on said pivot hereinafter referred to as a "spring clip device of the
kind described", Such devices are of use for the mounting of the flood
lights of photographic lighting outfits and spot lights for stage
lighting and many other purposes and should provide preferably for
movement in two planes in order that the light may be pointed in any
desired direction.
One of the difficulties hitherto experienced with such devices has
been to provide pivot means wherein the pivot is not too tight to
prevent the light, from being directed as desired and not so loose
that undesired movement will take place and the desired direction of
the beam cannot be maintained.
Moreover after some use the pivot often loosens and the device becomes
useless.
According to the present invention I provide a spring clip device of
the kind described wherein the clip is formed with a resilient base
which is flexed when said arms are spread and a co-operating friction
member is mounted on or formed in one with said supporting member for
engagement by said base said friction member having a contact surface
greater in all directions than the transverse dimension of the
narrowest IF Pri part of said base The supporting member may be a
bracket or may also comprise a clip and the friction member may
comprise any flat surface such as a disc or a circular area on the
supporting member which is adapted to be engaged by shoulders at the
base of the clip in all positions thereof on its pivot when said base
is arched by the spreading of the arms The said friction member may
comprise a disc freely mounted for rotation on said pivot or may be
formed integral with said supporting member.
Referring to the drawings filed with the Provisional Specification: -
Fig 1 is a perspective view of one form of device made in accordance
with the present invention.
Fig 2 is a side elevation of an alternative form of device.
Fig 3 is a perspective view of the bracket shown in Fig 2.
Fig 4 is an exploded view of the rivet and spring ring embodied in the
forms shown in Figs 1 and 2.
In the form shown in Fig 1 the spring clip device comprises two clips
2 and 3 of well known form each made from a continuous strip of spring

steel having a resilient base 4, shoulders 5 formed by doubling the
strip back on itself at the extremities of the base, and arms 6, said
base 4 having a length greater than the width of the strip, the said
clip 3 being pivotally mounted on and secured by its base to the base
of the clip 2 with a friction member formed by a stiff circular washer
7 of diameter substantially greater than the width of said strip
positioned between them and providing a contact surface for the bases
of said clips, said contact surface having a diameter subtially
greater than the wides of said strip stantially equal to the length of
the bases 4 of the clips The clips 2 and 3 and washer 7 are 79,T 300
held together by a common pivot pin 8, the pin 8, having a head 9,
being passed through holes pierced centrally in the bases 3 and
loosely positioned therein and in the example a illustrated, secured
by having a peripheral groove 10 adjacent to the free end adapted to
be engaged by a retaining spring ring 11 (Fig 3) also of known
construction The groove 10 is positioned to allow a little I 10 slack
in the joints so that there is no initial pressure of the bases 4 on
the washer 7 and the two clips turn freely on the pivot pin 8 until
the arms of one or both clips are spread Other forms of pivotal
mounting s and securing means may be adopted For example the end may
be lightly riveted over a washer.
In operation the clip 2 is positioned on a tube such as the tube 12
This spreads the } arms 6 of the clip 2 and arches its base 4 slightly
according to the degree of spread of the arms 6 so that those parts of
the base 4 adjacent the arms 6 are pressed into contact with the
washer 7 When the article to be mounted, for example, a spotlight bulb
13 is inserted into the Ci D 3 a similar reformation of its base 4
takes place and as the pin 8 prevents the bases 4 from separating more
than a limited amount, pressure is applied :30 by the bases 4 of the
two clips on the stiff separting member 7 adjacent the shoulders and
the friction thus obtained holds the two clips against turning with
relation to each other irrespective of their relative position.
It will be obvious that with the arrangement described the friction
member 7 is not gripped between the bases 4 until one or both have
been arched by flexing sufficiently to take up the slack in the pivot
8 It may be thought preferable in some cases to arrange that here is
no slack in the pivot and a light initial pressure is exterted by the
bases 4 on the washer 7-before the arms of either clip are spread Thus
the friction for retaining the lamp in the desired position is either
produced or increased when the arms are spread to receive the lamp 13
This construction enables a convenient o and easy adjustment to be
made of the spotlight bulb about the pivot pin 8 and the tube 12 so
that the beam is movable in two planes and may be directed as desired
within the limits thereby permitted.

a In the modified form seen in Figs 2 and 3 the supporting member
comprising the spring clip 3 and the large washer 7 is replaced by a
bracket 15 shown mounted on a wall 16 by a screw 17 the axis of which
lies fo in the plane generated by rotating the axis of the spotlight
bulb 13 about the pin 8 The bracket 15 has a circular washer shaped
portion 151 constituting the friction member.
This construction enables a convenient and easy adjustment to be made
of the spotlight bulb about the pin 8 and screw 17 so that the beam
may be directed as desired within the limits thereby permitted.
The modified form may be used to provide adjustable movement about
three axes if the screw 17 which also provides a pivotal connection is
engaged in the article to be mounted instead of a wall and the clip 6
is engaged on a supporting rod instead of the bulb 13.
( 55 710
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* GB785301 (A)
Description: GB785301 (A) ? 1957-10-23
Improvements in or relating to hods or scuttles for solid fuel
Inventor: -WILLIAM JOHN ADAM.
Date of filing Cotiplete Specsfi cation: June 14, 1955.
Application ate: June 14, 1954 No 17412/54.
Complete S'pecification Published: Oct 23, 1957.
Index at Acceptance:-Classes 52 ( 1), E; and 66, A( 2 B: 40: 6 B).
International Classificationl:-A 47 ij.
COMPLETE SPECIFICATION.

Improvements in or relating to Hods or Scuttles for Solid Fuel.
We, WILLIAM MALLINSON & SONS (MANUFACTURING) LIMITED, of Thames Road,
Crayford, Kent, a British Company, do hereby declare the invention,
for which we pray that a patent may be granted to us, and the method
by which it is to be perdformed, to be particularly described in and
by the following statement:-
This invention relates to hods or-scuttles (hereinafter called "hods")
for holding and carrying solid fuel, particularly fuel such as coke,
which is of relatively light weight and large bulk necessitating a hod
of substantial capacity in order to avoid frequent replenishment.
Hods for this purpose usually are made of metal, such as iron,
provided with a protective finish, such as a coating of paint or other
applied finish, such as "Sheradizing".
Apart from being relatively heavy and unattractive in appearance, they
are subject to deterioration in use, particularly the bottom, due to
rust or corrosion, which is hastened by the abrasive and corrosive
action of the contents, which rapidly wear through most protective
finishes.
The present invention has for its object to provide an improved hod of
attractive appearance which, for any given capacity, is relatively
light in weight, abrasion and corrosion resistant, strong, rigid and
durable.
It has before been proposed to produce buckets, casks and like vessels
of cylindrical or tapered formation by moulding two wall halves of
plywood in a press and applying strips over the contiguous edges to
hold the wall halves together It has also been proposed to produce
large vats, baths or the like having a marked conical shaje by
jointing two preformed parts by means of scarf joints, the joints
preferably being reinforced by means of straps.
It has also been proposed to produce laminated hollow bodies, for
example, lPric 1 boxes, wardrobes, cabinets and other forms of carcase
furniture by wrapping a plurality of disunited layers of veneer around
the perimeter of a mould or former to form a seamless body of
rectangular cross-section with rounded corners and bonding the
laminated assembly by an adhesive medium.
According to the present invention, a hod for solid fuel is provided
having a hollow parallel sided tubular body of rectangular
cross-section with rounded corners, comprising two complementary half
sections of laminated resin-bonded plywood joined together at the
contiguous edges, and a base member of similar material closing one
end of the hollow tubular body Preferably, the complementary half
sections are of channel formation and joined together at oppositely
disposed mating edges with lap or scarf joints Preferably also the
body is of substantially square cross-section The top of the hod is

preferably shaped so as to slope upwardly towards the mouth.
The base member preferably fits within the body and an external metal
reinforcement, e g of sheet aluminium or copper, may be flanged around
downwardly projecting edges of the body to reinforce the same.
The hod may be provided with suitable handles of resin-bonded plywood
or similar material.
The external finish of the hod may be varied by selecting a suitable
veneer, and if desired the external surface may be stained or
otherwise decorated.
Solid fuel, particularly coke, is very abrasive and it has been found
that resinbonded plywood, although relatively soft when compared with
a metal hod is far more resistant to abrasion Even if the inner
surface of the hod becomes scored by the fuel, it does not wear away
as rapidly as a metal hod; moreover it is non-corrodible and highly
resistant to damp.
785,301 so 785,301 The invention includes a method of producing hods
of laminated resin-bonded plywood, which comprises forming a tube of
rectangular cross-section with rounded a corners by jointing together
two complementary half sections of laminated plywood, cutting said
tube to provide sections, having one end in a plane perpendicular to
the axis of the tube and the other end shaped to provide a sloping
mouth, and fitting said sections with bases and handles, The tube may
be of a length sufficient to produce two bodies by sub-dividing the
tube diagonally with an S-shaped cut.
One embodiment according to the invention is hereinafter described
with reference to the diagrammatic drawings accompanying the
Provisional Specification, and in which:
Fig 1 represents a cross-section through a 2 i laminated plywood tube
from which sections t) form coke hod bodies are cut; Fig 2 is a
perspective view of a length of such tube showing the manner in which
it may be cut diagonally to form two complementary bodies; and Fig 3
is a part sectional perspective view showing in detail the mounting of
the handles and the location of the base.
In carrying the invention into effect oi according to one embodiment,
a length of substantially rectangular tube having rounded corners is
formed by jointing together two complementary halves 1 and 2 of
resin-bonded plywood, as shown in Fig 1, 3,5 preferably by means of
scarf joints 3 The scarf joints 3, instead of being parallel, as
shown, may be convergent.
Any suitable adhesive of known type may be employed for bonding the
joints of the tube Such adhesive must be water-resistant and fairly
heat-resistant since the hod is liable to be left standing in a warm
place near the fire.
Fig 2 shows a piece of laminated resin, bonded plywood tubing formed

as above described, which has been cut square at each end 4 and 5 to a
length sufficient to produce two identical body portions 6 by parting
the tube substantially diagonally ti with an S-shaped cut, as
illustrated by the dotted line 7.
In Fig 3, which shows a more detailed view, the body portion 6 has a
base 8 inserted into it, the base member preferably ,,5 being pinned
in position and bonded by a suitable adhesive The base 8 may be
inserted into the tube before it is parted into sections A bail-type
handle 9 is secured to the body by pivots 10 and may be pro: vided
with stop means to limit the swing of the handle on top of the hod,
the stop means, for example, comprising a shaped boss 11 at each side
which is either applied to, or incorporated in, the construction of l
5 the handle 9 At the side 12 of the hod opposed to the mouth a
moulded handle 14, also of resin-bonded plywood, is secured by bonding
and riveting.
It will be understood that the invention is not limited to the
particular embodiment 70 hereinbefore described.
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* GB785302 (A)
Description: GB785302 (A) ? 1957-10-23
Improvements in or relating to means for the estimation of small quantities
of gaseous impurities in rare gases
Improvements in or relating to means for the Estimation of Small
Quantities of Gaseous Impurities! in Rare Gases
We, THE BRITISH OXYGEN COMPANY

LIMITED, a British Company, of Bridgewater
House, Cleveland Row, St. Iames's, London,
S.W.1, do hereby declare the invention for which we pray that a patent
may be granted to us, and the method by which it is to be performed,
to be particularly described in and by the following statement:
This invention relates to methods of and means for estimating small
quantities of gaseous impurities in rare gases.
The rare gases as usualy produced are often contaminated with small
quantities of gaseous impurities. For example, the rare gases produced
as products of the separation of air, namely argon, krypton and xenon,
are frequently contaminated with small quantities of nitrogen, and
helium produced from natural gas is similarly often contaminated with
small quantities of methane.
For many uses of these gases, the presence of such minor amounts of
impurity is not harmful, but in certain applications the rare gas is
required in a high state of purity. For example, argon intended for
use as shielding gas in gas shielded arc welding must have a
relatively low nitrogen content and similarly there is a definite
upper limit to the amount
of methane tolerable in helium intended for use as a shielding gas.
Other common contaminants present in small quantities in commercial
rare gases are air and carbon dioxide.
The rare gases are inert and where the contaminant is also relatively
inert, as in the case
of nitrogen, it will be apparent that only methods based on physical
effects are likely to
be practicable for the estimation of the contaminant. Even where the
contaminant is relatively reactive chemically, physical methods are
still preferable on the grounds of speed and simplicity. The present
invention utilises the well known effect of traces of impurity on the
optical characteristics of a
silent electric discharge in the rare gas at low pressure. Thus, in
the case of argon/nitrogen, the discharge in pure argon is blue, but
the addition of nitrogen introduces a tinge of pink.
This phenomenon has previously been used to obtain a reliable decision
as to whether argon is spectrally pure by visual examination of the
colour of the discharge therein. It has now been found that this
phenomenon can also be made the basis of a quantitative estimation of
small quantities of gaseous impurities in rare gases.
According to the present invention, apparatus for the estimation of
small quantities of a gaseous impurity in a rare gas comprises an
electrical discharge tube, means for passing the impure rare gas at a
pressure substantially below atmospheric pressure through the
discharge tube, one or more photoelectric cells responsive to changes

in the optical characteristics of the discharge due to the impurity,
means for measuring the electrical output of said photoelectric cell
or cells, and compensating means for the output of said photoelectric
cell or cells due to the rare gas, said compensating means comprising
one or more additional photoelectric cells, responsive to the optical
characteristics of the discharge when pure rare gas is passed through
the discharge tube but not to the changes therein due to the impurity,
the additional cell or cells being connected in opposition to said
first mentioned cell or cells and exposed to the discharge from the
discharge tube.
The maximum impurity content which can be successfully estimated by
the method of the present invention will vary with each impurity and
each rare gas. Thus, for example, for nitrogen in argon the upper
limit is about 3000 volumes per million, since above this value, the
sensitivity of the method becomes low and concentrations of nitrogen
above 5000 volumes per million extinguish the discharge. For nitrogen
in helium, methane in argon or helium and air in argon or helium, the
upper limit is about 5000 volumes per million, while for carbon
dioxide in argon or helium, it is about 1000 volumes per million.
The changes in the optical characteristics of the discharge will also
vary with the components of the gaseous mixture concerned. As stated
above, the colour change caused by the addition of nitrogen to argon
is from blue to pink. In the case of nitrogen in helium, the discharge
in pure helium is straw yellow, the addition of nitrogen introducing a
tinge of pink into the colour of the discharge. In the case of methane
in argon or helium, the colour of the discharge is a brilliant light
blue which varies in intensity with the concentration of methane. The
addition of air to argon or helium causes the discharge to become more
pink, while with carbon dioxide the discharge is a brilliant
greenish-blue which varies in intensity with the carbon dioxide
content It is normally desirable to dry the rare gas prior to its
introduction into the silent electric discharge tube.
The discharge tube used may be of any convenient shape, but a
preferred tube is in the form of a glass tube bent to form a series of
sections of reasonable length, so as to give a long gas path without
becoinisig unwieldy.
For example, a glass tube of w inch diameter giving a discharge path
of 48 inches may conveniently be doubled on itself to form a bundle of
six sections, each 8 inches in length.
Preferably, all the sections in the bundle are arranged to lie in a
plane parallel to that of the active surface of the photoelectric
means so that the latter views a sheet of discharge.
The electrodes are preferably in the form of hollow metal cylinders
closed at one end, to which electric leads are attached and having

perforations to permit free circulation of gas.
The photoelectric means comprises one or more photoelectric cells, the
number required depending on the size of cell available. The discharge
tube and photoelectric cells are contained within a light-tight
casing, which may be lined with a reflective or diffusive material to
increase the intensity of illumination of the photocells and therefore
the sensitivity of the apparatus. The output from the cell or cells is
measured by a suitable instrument, which after calibration of the
apparatus may be fitted with a scale ruled directly with volumes per
million of impurity so as to make the apparatus direct-reading. The
sensitivity of the measuring instrument may be adjusted by means of
variable shunts so as to permit a full-scale deflection of the pointer
for various ranges of impurity content. These variable shunts may also
be used to compensate for changes in the electrical characteristics of
the photocells. In order to keep the scale as linear as possible,
resistance of the measuring instrument and of the shunts should all be
low, for example, less than 100 ohms.
One means for passing the impure gas through the discharge tube, which
forms a part or the apparatus according to the present invention is
illustrated in the accompanying drawing. It comprises a gas inlet 1,
connected ' OU311 a fine adjustment valve 2 with a branched tube 3.
One branch of tube 3 is connected through a lute 4 with a rotameter
type flowmeter 5 and the other through a capillary 6, a stop valve 7
and a liquid trap 8 with one end of the discharge tube 9. The other
end of the discharge tube 9 is connected by tube 10 through a stop
valve 11, and a fine adjustment valve 12 to a vacuum pump (not shown).
A vacuum gauge 13 is connected by tube 14 to tube 10 between valves 11
and 12.
In operation, the inlet 1 is connected to a source of the impure rare
gas at a pressure above atmospheric. The apparatus is then started up
by opening fine adjustment valve 2 (stop valve 7 being closed). The
gas then passes to waste through the lute 4 and rotameter 5. The
vacuum pump is then started and valve 7 opened. The gas stream
entering ihe gas inlet 1, after passing through the fine adjustment
valve 2 divides into two streams, one passing through the lute 4 to
the flowmeter 5 and thence to waste, and the other through the
capillary 6, stop valve 7 and trap 8 to the discharge tube 9. The lute
4 is intended to maintain a constant pressure head on the gas passing
through the flow control capillary 6 to the discharge tube 9. The
flowmeter 5 facilitates control of the excess gas passing to waste.
The pressure in the discharge tube 9 is controlled by adjustment of
the fine adjustment valves 2 and 12 and is measured by the vacuum
gauge 13.
The liquid trap 8, which is desirable but may not be essential in

certain analyses, and which may be cooled by immersion in liquid
oxygen or nitrogen or in a solid carbon dioxide/trichlorethylene
freezing mixture, serves to prevent traces of water vapor or lire
easily-condensible substances from being carried into the discharge
tube. It has the further advantage that it slightly increases the
colouration of the discharge and therefore the overall sensitivity of
the apparatus, and it also promotes initiation of the discharge when a
voltage is first applied to the tube 9.
The means described are intended to operate with a source of gas at a
pressure above atmospheric.
In order to obtain a true reading on the measuring instrument, various
compensations are required. In the first place, when a pure rare gas
is passed through the discharge tube, a current is indicated by the
measuring instrument. This can conveniently be neutralised by a
further photoelectric cell or cells, the exact balance being obtained
by adjusting a resistance in series therewith. These cells must have a
different spectral sensitivity curve from that of the main measuring
photocells.
It is found that the sensitivity of the apparatus falls with
increasing temperature, the coefficient in terms of volumes per
million per degree Centigrade increasing with increasing impurity
concentrations. This coefficient is almost proportional to the reading
of the measuring instrument and therefore, in theory, compensation
could be effected by including in series with the measuring instrument
a resistance with a high temperature coefficient.
However, in practice, apart from its undesirable effect on the
linearity of the scale and on the sensitivity, it is difficult to find
a material which has the requisite combination of low resistance and
high temperature coefficient. It is preferred, therefore, to effect
temperature compensation by the inclusion of an extra circuit This
temperature compensating circuit comprises a Wheatstone bridge having
three fixed resistance arms and a thermistor connected in the fourth
arm. The measuring instrument is connected in the galvanometer arm of
the bridge, so that the out-of-balance current will be added
algebraically to the photoelectric current. The E.M.F. applied to the
bridge is varied by means of a rheostat which has previously been
calibrated and has a dial marked in impurity concentrations. In
operation, an approximate reading of the impurity concentration is
made using any value of the out-of-balance current. The rheostat is
then set manually to the observed value of the impurity concentration,
whereby the necessary temperature compensating current is applied to
the measuring instrument.
If a significant change of impurity concentration occurs during the
setting of the rheostat, the final setting is adjusted to correspond

to the new reading of the impurity concentration.
The Wheatstone bridge has a relatively high resistance and therefore
does not affect the sensitivity or linearity of the apparatus.
It will be appreciated that the measuring instrument will need
recalibration for each different combination of gases and that,
similarly, adjustments will have to be made in the various
compensations.
When the impurity to be estimated is present in the rare gas in a very
small concentration, the sensitivity of the method of the present
invention can in certain cases be very considerably increased by
adding a small known amount of another impurity. This has the
unexpected effect of increasing the sensitivity by considerably more
than the algebraic sum of the concentrations of the two impurities.
For example, when estimating 10 volumes per million of nitrogen in
argon, the addition of 10 volume per million of carbon dioxide
increase the sensitivity and an apparent total impurity concentration
of about 30 volumes per million is observed.
What we claim is:-
1. Apparatus for the estimation of small quantities of a gaseous
impurity in a rare gas comprising an electric discharge tube, means
for passing the impure rare gas at a pressure substantially below
atmospheric pressure through said discharge tube, one or more
photoelectric cells responsive to changes in the optical
characteristics of the discharge due to the impurity, means for
measuring the electrical output of said photoelectric cell or cells,
and compensating means for the output of said cell or cells due to the
rare gas, said compensating means comprising one or more additional
photoelectric cells responsive to the optical characteristics of the
discharge when pure rare gas is passed through said discharge tube,
but not to the changes therein due to the impurity, said additional
photoelectric cell or cells being connected in opposition to said
first mentioned cell or cells and exposed to the discharge from said
discharge tube.
2. Apparatus according to Claim 1 wherein said discharge tube is in
the form of a glass tube doubled upon itself to form a bundle of
relatively short coplanar sections.
3. Apparatus according to Claim 1 or Claim 2 wherein said discharge
tube is provided with electrodes in the form of hollow cylinders
closed at the ends to which the respective electric leads are attached
and having perforations to permit free circulation of gas through the
electrode.
4. Apparatus according to any of Claims 1 to 3 wherein said means for
measuring the electrical output of said photoelectric cell or cells
comprises a direct-reading instrument.

5. Apparatus according to Claim 4 wherein the sensitivity of the
measuring instrument is adjustable by means of variable shunts.
6. Apparatus according to any of Claims 1 to 5 wherein said means for
passing the impure rare gas through the discharge tube comprises a
vacuum pump connected to one end of said discharge tube, apd fine
adjustment valve means adapted to maintain the pressure within said
discharge tube at a pre; determined value substantially below
atmospheric pressure, the other end of said discharge tube being
adapted to be connected to a source of the impure rare gas.
7. Apparatus according to Claim 6 wherein said discharge tube is
adapted to be connected to the source of the impure rare gas through a
cooled liquid trap.
8. Apparatus according to any of Claims 1 to 7 wherein means are
included for compensating for the effect of temperature on the
sensitivity of the apparatus, said temperature compensating means
comprising a thermistor adapted to measure the temperature and
connected in a Wheatstone bridge with three fixed resistance arms
means for applying an
E.M.F. to the bridge proportional to the impurity concentration as
measured without temperature compensation of the apparatus, and means
for adding tbe out-of-balance cur

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