“A weighed or measured portion of the sample is mixed with 5 c.c. of pure HCl (if the sample is alkaline it must be neutralised first), four drops of a 15 per cent. solution of cuprous chloride in hydrochloric acid are then added, and the mixture made up to 30 c.c. with water; if it is not convenient to work with such a small bulk as 30 c.c. this quantity may be doubled or trebled, but the same proportion of acid should be used. A rod of pure zinc, 3 cm. long and 5 mm. in diameter, is first placed in the flask, the above mixture is then introduced and the first cell placed in position; lead acetate solution 5 per cent. is now poured into the cell until it is about half full. The second and third cells are filled in a similar manner; a small tuft of cotton wool is introduced into the neck of the top cell, and its mouth capped with mercuric chloride paper, which may be held in position by an elastic band or a glass collar made from a piece of glass tubing. After forty minutes or more the cap is removed and examined in full daylight. A minute trace of arsenic is indicated by a lemon-yellow spot, which varies in tint according to the amount present; and a heavy trace by an orange-brown spot. The mercuric chloride paper is prepared as follows: one drop of a 5 per cent. solution of mercuric chloride is allowed to fall on the centre of a piece (4 cm. square) of thin Swedish filtering paper, such as Muncktell‘s No. 1 F.; the paper is dried before using.” The lead acetate in the cells absorbs any H₂S gas given off, and if additional cells contain a 15 per cent. solution of cuprous chloride in hydrochloric acid, PH₃ is also prevented from passing and causing a stain. By this method arsenic can be detected in the presence of 2500 times its weight of antimony. The presence of selenium and tellurium compounds does not interfere with the usefulness of this method.
Fleitmann‘s Test.—Detects arsenic in the presence of antimony, but does not detect arsenic as arsenic acid. When zinc or aluminium is heated with excess of potassium or sodium hydroxide in a mixture containing arsenious anhydride, arseniuretted hydrogen is evolved. The gas may be led into 4 per cent. nitrate of silver solution, or a test tube the top of which is covered with filter paper wet with nitrate of silver. The gas reduces the silver salt, and a black precipitate is produced in the solution, or a black spot on the paper.
Fatal Dose.—Two grains in solution have been known to cause death. Recoveries have, however, occurred after an ounce or more of the poison has been taken. Much will depend upon the fulness or emptiness of the stomach at the time the poison is taken, and also upon the vehicle in which the poison is administered. Vomiting and purging are more urgent when the dose is large, probably assisting to get rid of the arsenic before its fatal action is produced.
Fatal Period.—From twenty minutes to two or three weeks, and even later from the secondary effects of the poison. Any thick medium, cocoa or soup, will of course delay the action of the poison.
Treatment.—Vomiting should be promoted, and diluent drinks largely given. The stomach pump, if it can be procured without much delay, should also be employed to empty the stomach. Emetics of sulphate of zinc should be given without delay—followed by the administration of milk, lime-water, and albumen. Symptoms as they occur must be treated on general principles.
The hydrated sesquioxide of iron, the hydrated oxide of magnesia, and animal charcoal have been proposed and used as antidotes. The sesquioxide of iron can be prepared ready to hand by saturating the tincture ferri perchloridi with ammonia or washing soda. It should be given freely. Drachm doses of dialysed iron in water may be administered. Reputed antidotes are useless when the poison is in the solid state. The diarrhœa, tenesmus, collapse, pain, and nervous symptoms should be treated on general principles.
Other Poisonous Compounds of Arsenic
Arsenical Vapour.—The vapour from the flues of the copper and arsenic smelting-works in Cornwall, escaping into the air, may cause death to cattle, and the destruction of vegetation. The workmen in these works not infrequently suffer from eruptions on the skin, and from great constitutional derangement; but, on the whole, taking into consideration the dangerous nature of their employment, the men appear to enjoy average health. Actions for damage and nuisance have resulted from the escape of this vapour from the factories.
Arsenite of Potash.—A solution of arsenite of potash, mixed with the tincture of red lavender (the solution contains four grains of arsenious acid in one ounce)—better known as Fowler‘s Solution, or as Fowler‘s Mineral Solution or Tasteless Ague Drop. It is probably a solution of arsenious acid in carbonate of potash, and not a true arsenite of potash. This preparation has been much used as a domestic remedy for ague in the Fens of Cambridgeshire. Death from its use is rare; but it is, nevertheless, too dangerous a medicine to be used recklessly. Idiosyncrasy has much to do with the action of the drug, some persons taking even large doses with impunity, whilst, in others, the smallest medicinal dose has produced alarming symptoms. It is stated that the Styrian arsenic-eating peasant is capable of taking without injury five grains of arsenious acid for a dose; and in one case of suspected murder in Styria, the prisoner was acquitted as the deceased was known to be an arsenic-eater.
Donovan‘s Solution.—A solution of hydriodate of arsenic and mercury. Now officinal, and much used by many practitioners.