1911 Encyclopædia Britannica/Chlorpicrin
CHLORPICRIN (Nitrochloroform), C·NO2·Cl3, the product of the distillation of many nitro compounds (picric acid, nitromethane, &c.) with bleaching powder; it can also be prepared by the action of concentrated nitric acid on chloral or chloroform. A. W. von Hofmann (Annalen, 1866, 139, p. 111) mixed 10 parts of bleaching powder into a paste with cold water and added a solution (saturated at 30° C.) of 1 part of picric acid. A violent reaction is set up and the chlorpicrin distils over, generally without the necessity for any external heating. It is a colourless liquid of boiling-point 112° C., and of specific gravity 1.692. It is almost insoluble in water, but is readily soluble in alcohol; it has a sharp smell, and its vapour affects the eyes very powerfully. Iron filings and acetic acid reduce it to trimethylamine, whilst alcoholic ammonia converts it into guanidine, HN:C(NH2)2, and sodium ethylate into ortho-carbonic ester, C(OC2H5)4. The corresponding brompicrin is also known.