C₂HCl₃O,H₂O + NaHO = NaCHO₂ + H₂O + CHCl₃.
Trichlor-acetic acid is decomposed in a similar manner.
=Statistics.=--Chloral caused, during the ten years 1883-1892 in England and Wales, 127 deaths--viz., 111 (89 males, 22 females) accidentally, 15 (14 males, 1 female) from suicide, and a case in which chloral was the agent of murder.
§ 196. =Detection.=--It is, of course, obvious that after splitting up chloral into chloroform, the latter can be detected by distillation and applying the tests given at p. 152 and _seq._ Chloral hydrate is soluble in one and a half times its weight of water; the solution should be perfectly neutral to litmus. It is also soluble in ether, in alcohol, and in carbon disulphide. It may be extracted from its solution by shaking out with ether. There should be no cloudiness when a solution is tested with silver nitrate in the cold; if, however, to a boiling solution nitrate of silver and a little ammonia are added, there is a mirror of reduced silver.
§ 197. The assay of chloral hydrate in solutions is best effected by distilling the solution with slaked lime; the distillate is received in water contained in a graduated tube kept at a low temperature. The chloroform sinks to the bottom, and is directly read off; the number of c.c. multiplied by 2·064 equals the weight of the chloral hydrate present.
Another method, accurate but only applicable to the fairly pure substance, is to dissolve 1 to 2 grms. in water, remove any free acid by baric carbonate, and then treat the liquid thus purified by a known volume of standard soda. The soda is now titrated back, using litmus as an indicator, each c.c. of normal alkali neutralised by the sample corresponds to 0·1655 grm. of chloral hydrate. Small quantities of chloral hydrate may be conveniently recovered from complex liquids by shaking them up with ether, and removing the ethereal layer, in the tube represented in the figure.[182] The ether must be allowed to evaporate spontaneously; but there is in this way much loss of chloral. The best method of estimating minute quantities is to alkalise the liquid, and slowly distil the vapour through a red-hot combustion-tube charged with pure lime, as in the process described at p. 153. A dilute solution of chloral may also be treated with a zinc-copper couple, the nascent hydrogen breaks the molecule up, and the resulting chloride may be titrated, as in water analyses, by silver nitrate and potassic chromate.