Sesqui-mustard

Noteworthy in particular were German formulations of viscous mustard that were intended to confer long-term persistence on surfaces and to thwart efforts of decontamination. Like mustard formulations for winter use, some of the Zahlost types have arsenicals as major components. Thickening materials that were available up to 1945 (e. g. chlorinated rubber, waxes and polystyrene), added for powerful enhancement of viscosity, incidentally made the chemical agent formulations completely insoluble in the usual technically available solvents. 

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Agent HT is generally a mixture of 60% HD and 40% bis(2-chloroethylthioethyl)ether (T), although this ratio may vary. Agent HL is a mixture of sulfur mustard (HD) and lewisite (L) that was developed for cold weather or high-altitude use due to its lower freezing point. Sesqui mustard (Q) is l,2-bis(2-chloroethylthio) ethane and is considered a more potent vesicant than HD but its very low vapor pressure limits its effectiveness as a warfare agent,... 

Vocci FJ, Ballard TA, YevichP et al. (1963). Inhalation toxicity studies with aerosols of sesqui-mustard. Toxicol Appl Pharmacol, 5, 677-684. 

Sesqui-mustard, agent Q, QN2. Solid, Mp 56°C. volatility <1 mg/m3 at 20°C. British laboratory reported vesicant activity to be five times that of mustard gas and this may have been an underestimate. 

Agent T. Vesicant Mp 10°C. Like sesqui-mustard a low-volatility vesicant. Persistent. 

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