Mask breakers

Diphenylchloroarsine (DA), and diphenylcyanoarsine (DC), which both contain arsenic and are in the form of a powder at ambient temperatures, were used as mask breakers during WWI. The particles were able to penetrate the filters used at the time and could induce a soldier to break the seal of his mask allowing a more toxic agent such as phosgene to take effect. Diphenylchloroarsine and diphenylcyanoarsine were also mixed with sulphur mustard to lower the freezing temperature of the mustard. 

World War I. By this time, French military chemists used a mixture of 40 percent diphenylchlorarsine (a solid) and 60 percent phenyldichlorarsine (liquid solvent) as a mask breaker called Sternite. The former East German military chemist Siegfried Franke reports that German and Itahan armies stockpiled mustard mixed with phenyldichlorarsine in World War II. 

Because DA and related compounds cause intense effects on the nasal and upper respiratory passages, they are referred to as "sneeze gas" (sternutators). Like other arsenicals, DA is a white solid and was originally produced as both a casualty gas and a mask breaker during World War I. 

The concept of a mask breaker is sound, but the German design for its weapon failed to disseminate the agent into the air. Instead, most of the solid diphenylchloroarsine merely fell to the ground harmlessly in the area surrounding the explosion of its shell. In the rush to get blue cross agent shells into use, the German military failed to test... 

Diaryl Amines. The most active free-radical chain-breakers are diaryl amines. These generally discolor badly due to formation of quinoid structures, so they are not often used in plastics. In rubber, where the many C=C bonds create a great need for stabilization, and where carbon black generally masks any discoloration, diaryl amines are almost universally used. In plastics containmg carbon black, they may also be used very effectively. 

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