ARSENIC 511 mation of a double compound of silver arsenide and silver nitrate (AsAg3, SAgNOa). On the addition of water the yellow colour becomes black by the separation of silver. The colour produced by animony is not yellow, but brown or black. On the other hand, phosphoretted hydrogen produces the same colour as that of arsenic. In order to avoid this fallacy absorbent cotton is moistened with a solution of lead acetate. A modified form of Gutzeit test is used in which a dry paper permeated with mercuric chloride instead of silver nitrate produces a yellow stain, the intensity of which varies according to the quantity of arsenic present. 6. Bettendorff's Test.—This test can be used even when arsenic is present with antimony. It depends on the reduction of arsenic compounds to elementary arsenic by the action of stannous chloride in the presence of strong hydrochloric acid. It detects both inorganic and organic compounds of arsenic. When 2 cc. of the acid solution of the oxidized suspected material are added to 10 cc. of Bettendorff's reagent in a test tube, and the mixture is gradually heated, a brown, brownish-black or black precipitate is formed, if inorganic arsenic is present. When 1 cc. of the suspected solution is added to 3 cc. of the reagent in a test tube, a lemon-yellow precipitate or colour results, if the organic com- pounds of arsenic are present. Bettendorff's reagent is made by dissolving 1 part of crystallized hydrated stannous chloride in 10 parts of strongly fumhig hydrochloric acid. Medico-Legal Points.—1. Arsenic is used homicidally much more fre- 1 quently in India than in any other country, as it is cheap, is easily obtained ^ in every town and is easily concealed in the food in consequence of its free- dom from smell and taste. A very small quantity of arsenic is necessary to produce fatal effects, although cases have occurred, where much larger quantities were given for homicidal purposes. In a homicidal case that came under my observation in 1931, 101.6 grains of arsenic were detected in the stomach contents. In the year 1946 the Chemical Examiner of the Central and United Provinces detected 54.44 grains of arsenic in the portions of the viscera removed from the body of a sweeper who was administered arsenic in liquor, and 21.8 grains of arsenic in the vomited matter of a man who had been poisoned by his wife. Mass homicidal poisoning in which several persons have been affected has sometimes occurred from arsenic having been administered by an individual in some article of food. In a few instances, arsenic is administered with some other poison, such as powdered glass, copper sulphate, mercury, mercuric chloride, opium, aconite, mix vomica, etc. Instead of administering a single fatal dose of arsenic at once, the murderer in Western countries usually administers small doses over a long period in order to produce the symptoms simulating gastro-enteritis and thus to conceal the crime. Arsenic is sometimes employed as an al^grdfacient, both as an internal administration and as a local application in thelbrm of paste or ointment to abortion sticks. It is also use'd to poison cattle. Wells are known to have been poisoned by arsenic not only during war, but also in peace time. A case occurred at Nagpur, where the accused was stated to have added poison to water as it was being drawn from a well. A quantity of arsenic was found in the water.19 A bundle of cloth was recovered from a well in the district of Pubna. The cloth contained some dark grey coloured pasty substance which, on analysis, was found to be arsenic.20 19. UP. Chem. Exam. Annual Rep., 1907. 20. Beng. Chem. Exam. Annual Rep.; Ind. Med. Gaz.t Aug. 1915, p. SOS.