1) The document provides instructions for using an oxygen gas supply and conducting ozonolysis reactions. It details checking valves and pressure levels, opening gas cylinders, connecting regulators, and using catchpots and scrubbers to safely introduce ozone into reaction vessels. 2) Key steps include checking cylinder pressure, regulating pressure to 1 bar, using catchpots to prevent backflow between equipment, and maintaining positive pressure in reaction vessels using oxygen purges. 3) Safety measures like catchpots and scrubbers are employed to avoid hazardous gases from entering equipment or being vented without destruction.

1. These instructions detail the ease of using the oxygen gas supply.
1) Check all valves from gas inlet line on side of fume cupboard FC 02/10 to the ozone generators are
shut.
2) Outside, open main valve on gas cylinder by turning 45° anti-clockwise.
3) Check cylinder head pressure (0 – 400 bar gauge) is showing that cylinder still contains gas.
3.1) If at this point, the cylinder contains little of no pressure, the cylinder will have to be
replaced with a fresh cylinder. It is stated on the cylinder that the pressure of the full
cylinder will be at 230 bar at 15°C.
3.2) Close main cylinder valve by turning valve 45° clockwise or more until valve is shut.
3.3) There will be pressure between the main cylinder valve and the regulator valve due to
residual pressure in the cylinder and this will need to be relieved. Under no
circumstances try to unscrew the main regulator head from the cylinder at this point.
This may result in injury and damage to the oxygen line leading into the building.
3.4) Turn regulator valve till the delivery pressure is at around 1.0 bar. At this point the
gas line going into the building will be under 1.0 bar pressure.
3.5) Inside, the line pressure gauge to the ozone generators should be equal to that of the
pressure outside on the regulator’s delivery pressure gauge, 1.0 bar +/- 0.25 bar.
3.6) There is 2 gas lines to the ozone generators which are both operated by valves on the
side of fume cupboard. If both lines are connected to the ozone generators, remove
one oxygen delivery line to one of the generators.
3.7) Turn the valve corresponding to the disconnected gas delivery line gently to open to
release the oxygen contained within the line work. This should be proceeded by a
large ‘hiss’ that subsides after a few seconds.
3.8) Shut the gas delivery line valve as the oxygen line is now ‘relaxed’ and not under
pressure.
3.9) Return outside and the delivery pressure gauge should now be at zero. Checking to
make sure the main valve on the cylinder head is completely closed, adjust the gas
delivery pressure valve so the valve is closed. The regulator head can then be
unscrewed form the main cylinder head.
3.10) Remove the cylinder from the support against the building and rest in a cylinder
carrier. If the cylinder had a valve cover, it is best to remove it. The BOC delivery
man will not check to see if a cylinder is empty, but if you choose to cover the main
cylinder head valve with the valve cap, even if it is placed in the ‘empty’ rack, it
looks like a full cylinder!
3.11) Having returned the empty cylinder to the empty rack and before retrieving an
apparently full cylinder, check the appearance of the main cylinder valve head. A
new unused cylinder head supplied by BOC or any other reputable supplier with have
a valve cover and have a plastic wrapping around the valve cover to avoid
contamination and ingress of dirt into the valve. If the main cylinder head valve has
no cover, leave it. Checking for pressure in the cylinder by turning the main cylinder
head valve slightly open will result in release of oxygen or residual oxygen as it may
be, but there is no indication from this of the cylinders pressure. If no other cylinder
is present which has the valve head wrapped up and only one with the valve head
exposed, take this one.

2. 3.12) In a reverse of step 3j, using the cylinder carrier, place the upright ‘chained-up’
cylinder as close to the building as possible with the support leg of the cylinder
carrier extended and secured. Release the cylinder from the carrier and move against
the support of the R&D building and secure it there.
3.13) Remove any valve head wrapping and any valve cap that may covering the valve
head. If the cylinder hasn’t got these attached, it is good practise whether the valve
head has been covered or not to remove debris such as dust from the valve head with
a ‘blast’ of oxygen from the cylinder. This is simply done by turning the main
cylinder head valve slightly till a weak blast of oxygen is expelled. The cylinder is
now ready to be attached to the gas regulator valve.
3.14) Position the gas regulator valve union over the gas cylinder valve and bring them
both together. Using only your hands at first, screw down the nut above the gas
regulator union into the gas cylinder valve thread. It may not to screw down
immediately because it is misaligned so adjust the gas regulator head until the gas
cylinder valve thread is found with the union nut.
3.15) When the union nut has been screwed down as far as physically possible to ‘finger-
tightness, further tighten the union nut with and adjustable spanner. When it has been
tightened as far as possible, a seal has been formed from the union in the gas cylinder
valve. The oxygen gas is now due to go ‘live.
3.16) Any hissing that is heard from the connection between the gas regulator and gas
cylinder indicates a bad seal has been formed. Even if no hissing is heard, it is good
practise to use distilled/deionised water around the top of the screw thread thus
making a crude seal between the gas regulator and the gas cylinder. If bubbling is
observed, however slight, this indicated a bad seal.
3.17) If no bubbling is observed., a good seal is formed. In the event of a bad seal, repeat
steps 3.2 to 3.9 followed by 3.14 to 3.16. repeat until no leak is observed. If after
several attempts at solving the oxygen gas leak, it may help to clean the union with a
damp cloth moistened with water. But ensure the union is dry before trying to
attempt to reform a seal.
4) Having observed there is pressure indicated by the cylinder head pressure on the gas regulator
head and no leaks, go inside and check the valves to the ozone equipment are shut. Then return
outside and adjust the gas regulator head to 1 bar pressure. The oxygen gas line into the building is
now ‘live’. The line pressure gauge on the side of FC02/10 should also read about 1 bar.
5) By connecting the one of the oxygen delivery lines to either piece of equipment and opening the
respective valve on the side of the fume cupboard, the ozone equipment is now under 1 bar
pressure from the oxygen line.
6) Operation of both pieces of equipment to activate the production of ozone is different, but both
oxygen gas delivery lines to the ozone generators must go via a catch-pot. This is to ensure any
moisture that condenses in the oxygen gas delivery line during cold spells of weather is caught in
the catchpot. Moisture or condensed air will also contain trace amounts of air: nitrogen entering
the ozone generator is capable of oxidising to oxides of nitrogen which may further go on to form
acidic fumes, in the worst event a small amount of nitric acid inside the generator. On another
note, it prevents anything being drawn back into the oxygen gas delivery line from the generator.
7) From the generator to the ozonolysis vessel, another catchpot and cold-trap are used. The catchpot
is to prevent the contents of the ozonolysis vessel being drawn back into the ozone generator. It
also possesses a blue/grey haze when the ozone generator is in use which is a further indicator of
the ozone generator producing ozone as the ozone must first pass though this vessel before
entering the ozonolysis vessel. The cold trap is installed to cool the stream of ozone being added to
the ozonolysis vessel. In somecases, the dielectrics inside the ozone generator may warm up and
this heat is taken in by the ozone gas stream. A cooler gas stream ensures exotherms are minimised
in the ozonolysis vessel.

3. How to start up an Ozonolysis with minimum disruption.
1) Ozone reactions will commonly be undertook at temperatures below 0°C. This is mainly because
a) ozone is more soluble in cold mediums, b) ozonolysis commonly produces exothermic reactions
and c) there is evidence that suggests ozone breaks down at ambient temperatures of around 20°C.
2) When charging the vessel, it is advised to have a small oxygen purge on the vessel. As the
ozonolysis vessel’s vent line is connected to a pair of in-line ozone scrubbers. The first acting as a
suck-back trap and the second containing 2 parts 37% w/w Sodium Metabisulphite, 2 parts water
and 1 part 25% w/w Sodium Hydroxide. To prevent the second scrubber being ‘sucked back’ when
the ozonolysis vessel and its contents are cooled back, the headspace of the ozonolysis vessel is
purged with oxygen and this is of course vented via the scrubbers maintaining a positive pressure
in the vessel.
3) Failure to operate an oxygen purge results in the ingress of air into the ozonolysis vessel via the
scrubbers. They may result in unwanted side reactions due to moisture in the ozonolysis vessel. It
also means the contents of the second scrubber vessel is sucked back into the first vessel. The
suck-back trap performs as it was designed but this also means when the ozone gas stream is
sparged into the ozonolysis vessel, the waste gas stream that is vented off has to displace the
scrubber solution that has been sucked back into the first scrubber to form a positive waste gas
stream flow though the scubbers. This in turn forms pressure in the vessel’s headspace. This can
lead to blowing the first scrubber inlet when it overpressurises or in the worst case scenario, if the
gas stream is inadvertently stopped, the pressure in the vessel forces the pot contents back up the
ozone gas stream sparge line. The use of the catchpot utilised between the ozone generator and
ozonolysis vessel prevents the ozonolysis vessel contents entering the ozone generator.
4) When the ozonolysis vessel is cooled sufficiently to its operating temperature, by simply
increasing the flow rate and powering on the ozone generator, ozone is produced and is sparged
into the pot at the desired temperature. The waste gas stream is vented via the scubbers were it is
destroyed before any waste gases entering the atmosphere.
5) At the end of the ozonolysis after the ozone has been purged from the ozonolysis vessel with
oxygen, it is advised to again maintain a positive pressure on the vessel during the holding of the
experiment at low temperatures.