The Chemical Warfare Agents

Some of the agents were only present as laboratory scale samples and were held for testing purposes. Other were held in bulk in case a retaliatory strike was necessary. By the end of the war a vast array of chemical warfare agents had been imported.

The three most common chemical warfare agents imported were mustard gas, phosgene and Bromobenzylcyanide. They are considered in turn. Other agents imported included Lewisite (by the Americans), Cyanogen Chloride, Hydrogen Cyanide (Prussic Acid), Adamsite and Chloropicrin amongst others.


Pure mustard gas [bis (2‑chloroethyl) sulfide/2,2′ – dichloroethyl sulphide] has a melting point of 14 degrees celsius and is thus a heavy oily liquid in temperate and tropical climates. It has a reddish/brownish (amber)  appearance Mustard gas has the power of burning and blistering any area with which it comes in contact, either as liquid or vapour, whether within the body or on the surface.

Depending on dose, it can severely impact the eyes, the entire respiratory and digestive tracts and destroy white blood cells. It affects all tissues with which it comes into contact.

 Yeah, well mustard gas it’s a sort of a viscous liquid.  Not quite colourless, got a bit of a yellowy look to it, yellowy green.  Doesn’t look like it’d do you any harm.  Smells of onions, we were never allowed to eat onions or have onions served to  us.  I didn’t like onions anyway, so it didn’t worry me all that much! [Ivor Conway (Chemical Warfare Armourer)]

According to the mode of delivery (eg; bomb or spraying) the mustard gas was modified so to enhance its effectiveness. The two most common variants were Y3 (HT) and Y4 (HTV). Chemical Warfare Agents were given a Code Symbol but were also marked with a different code on the munition itself to prevent identification. Y3=Code Marking on a munition which contained this material and HT= the code symbol.

Y3 (HT)

Standard British Mustard gas containing 60 percent mustard (dichloro-diethyl sulphide) and 40 percent T724 (itself an agent that raised blisters) prepared by the thiodiglycol process. Classed as the most stable form of mustard gas. By far the most common mustard variant the Royal Australian Air Force  had in its arsenal. It had 97,633 bulk gallons at 1 May 1944 and used it as the fill for most of its munitions. It was actively used in a number of trials including those with 65 lb bombs.

Y4 (HTV)

Thickened Y3 mustard gas which was used for spraying from aircraft. If it was not thickened the droplet size of the mustard was too small and it simply drifted too far from the target area. The thickening agent in Y4 involved the use of chlorinated rubber. It was the most common variant the Australian Army possessed in its stocks and was found in 25 pounders and 6 inch howitzer shell and had a “shelf life” of at least 3 years. 449 tons had been shipped to Australia by March 1943 (with 151 tons ‘outstanding’). The RAAF had 58,283 bulk gallons at 1 May 1944 and used it as a fill for its Smoke Curtain Installation spray tanks.

The other Y4 variants eg: Y4a, Y4b and Y4c had polyvinyl acetate or Perspex (polymethyl methacrylate or methyl methacrylate, coded MM), rather than chlorinated rubber added. This was because the rubber supplies were in short supply (as the Japanese had captured Malaya, its main source) and rubber, designed for a temperate climate did not perform well in Australia’s tropical climate.


Carbonyl chloride. Fog like in initial concentration, becomes colourless as it spreads and has an odour like musty hay. Highly toxic. Affect primarily the respiratory tract ie: the nose, throat and particularly the lungs. Swelling of the membranes can lead to the lungs being filled with liquid and possibly death (sometimes known as “dryland drowning”). At low temperatures it forms a colourless liquid, and it is usually stored in this form. The liquid actually bolls at just over 46 degrees Fahrenheit, and this is why it evaporates as soon as it is liberated from a bomb or cylinder. The gas is invisible, but when it is first released its cooling effects condense the moisture in the air and a whitish mist can often be seen for a few moments.

It was used in 250 lb Royal Australian Air Force bombs and also used as a chemical fill for the Army’s 4.2 inch mortars and 5 inch rockets.

Noel Stoneman (Chemical Warfare Armourer) discusses his exposure to phosgene when emptying 250 lb phosgene bombs at No. 19 Replenishing Centre at Talmoi, Queensland;

When [the] war finished and there was no need to keep these stocks, it was decided to dispose of all stocks of chemical warfare [at Talmoi].  In particular the phosgene gas, which I had 28,000 250-lb bombs under my charge.  The means of disposing of those, was to stack them up like a heap of barrels and shoot a 303 shot or bullet into the rear end of every bomb.  That relieved the pressure of the phosgene inside which boiled at 60º and it squirted out like steam out of a steam engine.  It wasn’t long  out of pressure and it vaporised that it was invisible.  This invisible cloud, could then lay in any hollow or moist area and after having this shooting party which, on one particular occasion I was in charge of, and I had stepped back and we’d inspected that they all had holes in them and we’d stepped out of what we thought was the cloud of gas.  I inserted two fingers in beside my respirator and took a breath, and found  that the air was clear.  I then kept on walking, and then…. took my respirator off.  But unfortunately [I] walked into a cloud of phosgene gas, which I didn’t realise was there and immediately was into this cloud and immediately started coughing very severely.  The CO [Commanding Officer] was there, plus several others and the immediate treatment for that was to lay down and relax, which they insisted I do.  But they still had respirators on, but I didn’t.  So I’m coughing and choking and my CO came along and said, to lay down and then he more or less sat on me, but I was giving him such a struggle that he took his respirator off and realised the damage that was happening, that I was in this cloud of phosgene gas.  He got off me and of course, I immediately jumped up and ran, which was one of the worst things I could have done.  After that accident, the CO said, well you’re going to have to go to hospital, which they took me in by rail trolley, 30 mile, into Richmond, from there was a Fettlers settlement five mile down the line.  And they brought this trolley up on the line and I can’t remember whether it was a motorised trolley or one of these hand driven trolleys, but they took me into Richmond Hospital, whereby I was admitted for a few days, I can’t remember exactly because I wasn’t in the best of condition at that stage.  Eventually when I was discharged from the hospital, as good enough, I was sent then down to Lithgow, to be sent for discharge from there. Because  Lithgow was actually our chemical warfare headquarters.


Bromobenzylcyanide is 70% phenylbromacetonitrile and 30% phenylacetonitrile as diluent. Introduced by the French in July 1918 (World War I). A strong eye and respiratory irritant inducing headache, nausea and smelling vaguely like rotten fruit. Invisible vapour.

The chlorinated rubber thickened variety B4 (BBCV) was used to fill 85,758 – 25 pounder Base Ejection Army shells.