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$ 97. Another method for the detection of phosphorus in cases of poisoning has been given by Mitscherlich (Journal für Pract. Chemie, vol. lxiii., p. 238.)
The suspected substance is introduced, together with some sulphuric acid, and the necessary quantity of water, into a small flask (A. Fig. 11.) Into the neck of the flask a long horizontal delivery-tube (b) is fastened by means of a perforated cork; the other end of the tube (b) is bent at a right angle, and enters through a cork into the vertical condensing-tube (c)
of a Mitscherlich's condenser. The condenser consists of a tall glass-cylinder (B) perforated at the bottom; through this opening passes the lower, conical end of the condensing-tube; it is fitted in by means of a perforated cork. The cylinder rests on a wooden tripod perforated in the centre. From a vessel (D) a current of cold water is made to flow through the funnel tube (i) to the bottom of the cylinder (B); the hot water rises to the top and escapes through the tube (g) which, by means of a cork, is inserted into an opening at the upper part of the cylinder. A flask (C) serves to collect the distillate. The flask (A) is then heated until distillation com
If phosphorus is contained in the contents of the flask, a distinct luminosity, usually a luminous ring, is observed in the dark at the spot where the vapors enter into the upper part of the tube (c). When a mass, weighing five ounces, and containing only to of a grain of phosphorus, i. e. Tootooth part, is thus treated, the luminosity will continue until about three ounces have distilled over, which will take about half an hour. In an experiment, executed in this manner, the distillation was discontinued at this period, and the flask, uncovered, left to rest for fourteen days; when the distillation, after this time, was resumed, the luminosity appeared as before.
If there are in the liquid substances which destroy the luminosity of phosphorus, as ether, alcohol, and oil of turpentine, no emission of light is perceptible as long as these distill over. In the case of ether and alcohol, which are very volatile and pass over very soon, the luminosity appears after a short while; but if oil of turpentine is present, the phenomenon cannot be observed.
At the bottom of the flask which receives the distillate, the phosphorus collects in small globules. In an experiment, where five ounces of substance, containing one-third of a grain of phosphorus, were treated after this method, so many globules of phosphorus were obtained, that one-tenth part of them sufficed to prove them to be phosphorus. One portion of the globules may be thrown on a filter, and washed with alcohol; on being then placed on a warm spot, the phosphorus melts and ignites spontaneously. Another portion of the globules, and the liquid which, on distillation, exhibits luminosity, may be handed to the authorities.
If large quantities, containing a considerable amount of phosphorus, are subjected to distillation, sufficient phosphorous acid is produced (by oxidation of the phosphorus vapors), that its presence in the distillate may be detected by nitrate of silver and protochloride of mercury; or it may be converted into phosphoric acid by oxidation with nitric acid.
Mitscherlich observes that no importance ought to be attached to the reactions which the distillate may give with nitrate of silver and protochloride of mercury, since volatile animal matters, which also act reducing on these salts, may condense in the receiver. He also observes that, on distilling from a retort, the contents of which are kept boiling, it cannot very well be avoided that some particles of the liquid are carried over mechanically into the receiver, and thus the distillate may become mixed with phosphoric acid.
ON THE DETECTION OF ALCOHOL AND CHLOROFORM.
$ 98. The detection of alcohol in the body, in cases of death from alcoholic liquors, will, as a general thing, be more of scientific than of practical interest. The investigation will always be successful if commenced soon after death, or if the substances for examination, contents, lungs, etc., were preserved in well-closed vessels. It is good to have the vessels tied over with bladder.
The first thing to be observed is the odor and the reaction of the substances under examination. The contents of the stomach of persons who died of the effects of alcohol, show usually a decided acid reaction, owing to the presence of acetic acid. In this case, the acid is neutralized with carbonate of soda, avoiding an excess of the alkali.
The mass is then placed in a retort which is heated over a water-bath. The retort is connected with a receiver, or better, with a refrigeratory. The. distillate is rectified by a second distillation with addition of a sufficient quantity of dry carbonate of potassa, or chloride of calcium. For this second distillation, a small tubulated retort may be used, or a sinall flask, into the neck of which a long, bent glass-tube, of several feet in length, and from one-quarter to one-third of an inch in diameter, is fitted by means of a perforated cork. The tube must be of thin glass and bent at its lower extremity, in such a manner as to reach into a small glass-bottle, for the reception of the distillate. The tube is surrounded by blottingpaper, which is constantly kept wet with water, and thus serves as a condenser. Into the flask, or retort, first the liquid, then the carbonate of potassa, or chloride of calcium, is introduced. A large porcelain dish may serve as a water-bath.
No rules can be given as regards the quantity to be distilled over; this must be left to the judgment of the analyst.
$ 99. If the distillate does not contain too small a quantity of alcohol, it is already detected by its odor. But whether the odor is noticed, or not, the distillate. should be subjected to the following tests :
When poured on a hot plate, or when heated in a platinum-spoon, it burns, even if but little alcohol is present.
When heated with chromic acid, or with chromate of potassa and sulphuric acid, the chromic acid is reduced, sesquioxide of chromium is formed, and the liquid assumes a green color. If the operation is performed in a small retort, which is connected with a well-refrigerated receiver, a liquid containing aldehyde is obtained ; on heating this liquid with caustic soda, it assumes a yellow, or brownish color, and emits a peculiar, cinnamon-like odor.
A small portion of the distillate is poured on a porcelain plate, on which a watch-crystal is placed, which contains some platinum-black, free from acid.