This document discusses different types of viscometers used to measure viscosity. It describes single point viscometers like the Ostwald viscometer that are suitable for Newtonian fluids and measure viscosity at a single shear rate. Multipoint viscometers like the cup and bob viscometer can measure viscosity at various shear rates and are required for non-Newtonian fluids to obtain the entire viscosity curve. The document explains key viscometers like the Ostwald, cup and bob, cone and plate, and their working principles based on equations like Poiseuille's law.

1. Determination of
Viscosity
- By Sourabh Chauhan

2. Name : SOURABH TARAKESHWAR CHAUHAN
Class : S.Y.B pharm
Roll no : 18
Division : A
Subject : Physical pharmaceutics – Ⅱ
College: Shree D.D. Vispute college of Pharmacy and research
center, gate no-04, vichumbe, new Panvel.

3. Determination of viscosity:
In case of Newtonian systems the rate of shear is directly
proportional to the shearing stress.
Therefore, single point viscometer i.e. the equipment that works
at a single rate of shear, is sufficient.
For evaluation of Non-Newtonian fluids multipoint viscometers
are required, because the apparent viscosity is to be determined at
a several of rates of shear to get entire consistency curve.

4. Viscometer
 Single point
 At a single rate of
shear one point on
the curve
 Equipment:
Ostwald viscometer,
Falling sphere
viscometer
 Application:
 Newtonian Fluids
Multipoint
Several rates of shear
many points on the
curve
Equipment:
Cup and bob
Cone and plate
Application:
Non Newtonian fluids &
Newtonian Fluids

5. •CAPILLARYVISCOMETER
•Also known as U-tube viscometers, capillary
viscometers include the Ostwald and
Ubbelohde variations.
•They’re straight-forward and simple to use,
consisting of a U-shaped glass tube with two
bulbs (one higher and one lower).
•Fluid passes from the higher bulb to the lower
bulb through a capillary, and viscosity is
measured by timing how long it takes the
fluid to pass through the tube

6. Introduction:
These viscometers are suitable for
only Newtonian systems.
Principle:
Capillary Viscometer based on Poiseuille’s law. This method of
measurement, Measures time taken for defined quantity of fluid to flow
through a capillary with known diameter and length. It is then
compared with time required to flow by a liquid of known viscosity
(usually water) .
The viscosity of unknown liquid can be determined by using equation:
η1/η2= ρ1t1/ ρ2t2

7. η1/ η2= RELATIVE VISCOSITY OF LIQ.
The above eq. is based on POISEUILLE’S LAW for liq.
flowing through capillary tube
η= π r⁴tΔP/ 8lV
Where, r = radius of inside capillary t= time flow
ΔP=Pressure under which liq. Flow
L= length of capillary
V= Volume of fluid flowing
This e.q can also be written as
η= KtΔP

8. Capillary Viscometer
Ostwald viscometer Suspended level
viscometer
Couette type Or revolving
cup type or Mac Michael
viscometer
Searle type or revolving
bob type or stormer
viscometer

9. •OSTWALD’S VISCOMETER:
•Ostwald’s viscometer also known as U-tube viscometer
•A device which is used to measure the viscosity of the
liquid with a known density. This device is named after
“Wilhelm Ostwald
Working & Principle:
The viscometer is filled with liq. Upto bulkA through 1 st arm.
Then suck the liq. Through 2 nd arm to upper point C of the bulk B .
Now allow the liq. To pass from upper marked C to lower marked D.
And note the time of flow from upper marked C to lower marked D.
Now the viscosity of liq. Can be calculated by using formula;
η1/η2= ρ1t1/ ρ2t2

11. FORMULA:
Viscous drag on body = force responsible for the
downward movement, thus :
3пηdv = п/6d³g x Ps– P1
where,
D = diameter of the sphere
g = acceleration due to gravity v = terminal velocity
Ps = density of sphere P1= density of liquid by
rearranging formula :
η = d²g ( Ps – p1 ) / 18v

12. •CUPAND BOB VISCOMETER:
•This is a multipoint viscometer and belongs to the category of rational viscometer.
•It is consist of two coaxial cylinders of different diameters.
•The outer cylinder forms the cup into which the inner cylinder or bob is fixed
centrally.
•The torque set up in the bob is measured in terms of angular deflection Q of a

13. Couette type Or
revolving cup type or
Mac Michael viscometer
Searle type or
revolving bob type or
stormer viscometer
TYPES

14. COUETTE TYPE VISCOMETER
•In this the cup is rotated and the viscous drag on the
bob produced by the liquid results in a torque which
is proportional to the viscosity of the liquid.
•Example:
MacMichael viscometer

15. SEARLE TYPE VISCOMETER
•In searle type viscometer, the bob is rotated while the cup is
held stationary. Examples: Stormer viscometer &Brookfield
viscometer
•FORMULA
η=kv w/v
Where
Kv =instrument constant
W=weight in gram
V=rpm generated due to w

16. •CONEAND PLATE VISCOMETER
•Acone-plate is precise torque meter which driven as discrete
rotational speed.
•The torque measuring system which consist of a calibrated
beryllium copper spring connecting the driven mechanism to rotating
cone, sense of resistance to rotation caused by
presence of sample fluid between the cone and stationary flat plate

17. Thank You