Observations on Reinsch's test for arsenic / by William Odling.

  • Odling, William, 1829-1921.
Date:
1800-1899
Catalogue details

Licence: Public Domain Mark

Credit: Observations on Reinsch's test for arsenic / by William Odling. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    2/12
    must have regard, firstly, to the smallest quantity of the poison that can be satisfactorily determined under favorable conditions; secondly, to the effect of dilution, and other circumstances, in interfering with the determination of this quantity. As regards the former inquiry, I have repeatedly found, in confirmation of Dr. Rainey’s experiments, that y^th of a grain of arsenious acid will give, in succession, a deposit upon copper gauze, an obvious crystalline sublimate, and a brick-dust coloured pre- cipitate of arseniate of silver. When the test is performed in the ordinary manner, but with less than y^th of a grain of arsenious acid, the production of a crystalline sublimate, and brick-dust precipitate, is unsatisfactory; though the deposit upon copper may be obtained from much smaller quantities. Nevertheless, the practical application of Reinsch’s test is not absolutely limited to the detection of y^th of a grain of arsenious acid, as shown by the following experiment. The ^_th part of a grain of arsenious acid was dissolved in a mixture of three fluid drachms of water with one fluid drachm of hydrochloric acid, sp.gr. IT6. A small piece of Dr. Taylor’s fine copper gauze was introduced, and the whole boiled in a long- necked flask. In the course of ten minutes, a decided discoloration of the copper was produced. The ebullition w7as continued for half an hour, by which time there was a very obvious deposit. The copper was then removed, washed, and dried. Thus, ^t_th of a grain of arsenic was clearly perceptible in the state of metal; but in order to render it visible in the state of crystal- line arsenious acid, it was necessary that the sublimate should be confined to the smallest possible space, and not be spread over the entire circumference of an ordinary-sized reduction- tube. An appropriate subliming tube was made as follows : A piece of clear, hard, German tubing, a couple of inches long, with a bore of about one eighth of an inch in diameter, was drawn out at one end, so as to form an almost capillary termi- nation of about an inch in length. The piece of coated gauze was folded up, and introduced at the other extremity of the tube, which was then sealed by the blowpipe; care being taken to keep the copper as far removed as possible from the heated extremity. After cooling, the copper was tilted back to the sealed extremity, and the heat of a spirit-lamp applied to the whole body of the tube, commencing at the open capillary