Pharmacologia / Fourth American, from the Seventh London Edition

by John Ayrton Paris

[413]. This opinion has lately received ample confirmation from the experiments of Dr. Christison, (Edinb. Med. and Surg. Journal, July, 1824) who has shewn that the process of Orfila is objectionable on the three following grounds, viz.

1st. The colour is very seldom so entirely destroyed but that the precipitates produced by some of the tests still deviate to a certain degree from their characteristic tints; and although the colour of the fluid be even destroyed entirely, it often re-appears in the precipitates.

2d. Although the Chlorine destroys the colour, it does not also take from the fluid its solvent action on the arsenical precipitates.

3d. In fluids decolorized by Chlorine, and containing no Arsenic, some of the tests produce precipitates, not only precisely the same with those which they cause in the decolorized solutions of Arsenic, but likewise very similar in appearance to those caused in a pure aqueous solution of Arsenic.

[414]. The experiments by which I ascertained this fact were made soon after the publication of Mr. Phillips’s paper, and long before I saw Dr. Christison’s communication in the Edinburgh Journal. I merely mention this circumstance to add greater weight to the experimental evidence, for when different persons arrive at the same conclusion without any communication with each other, the strongest possible testimony is afforded. I may also add that my suspicions were raised to the probability of the fact by a knowledge of the action of charcoal upon lime water. In a philosophical point of view the fact is one of great interest; it seems to connect the phenomena of mechanical and chemical attraction. We have evidently a body removed from the state of solution by mechanical means.

[415]. The following is the formula for its preparation. Dissolve ten grains of lunar caustic in ten times its weight of distilled water, to this add, guttatim, liquid ammonia, until a precipitate is formed: continue cautiously to add the ammonia, repeatedly agitating the mixture until the precipitate is nearly redissolved. The object of allowing a small portion to remain undissolved is to guard against an excess of ammonia. Wherever the test is used, the liquid to which it is added ought to be quite cold.

[416]. This is very important, for an excess of ammonia redissolves the yellow precipitate, and therefore defeats the object of the test. The fixed alkalies, in excess, have not such a property.

[417]. The great impression made upon the public mind in Cornwall, by the above trial, produced a disposition to regard the cause of every sudden death with more than usual jealousy. See a Report of this trial in the Appendix of our work on Medical Jurisprudence.

[418]. In consequence of a report having arisen that a young woman had died after an illness of forty-eight hours, and been hastily buried at Madron, the magistrates of that district issued their warrant for the disinterment of the body, and requested my attendance at the examination. It appeared upon dissection that the immediate cause of death had been inflammation of the intestines; the stomach was found to contain a considerable portion of liquid, which was carefully collected and examined; no solid matter could be discovered in it. It appeared to consist principally of the remains of a quantity of penny-royal tea, which had been the last thing administered to the deceased. This was divided into several portions, and placed in separate wine glasses, and submitted, in the presence of the sheriff and other gentlemen, to a series of experiments, amongst which the following may be particularized, as bearing upon the question at issue.

1st. A few drops of a solution of sub-carbonate of potass were added to the liquid, in one of the glasses, when its colour, which was before of a light hazel, was instantly deepened into a reddish yellow; the sulphate of copper was then applied, when a precipitate fell down, which every one present immediately pronounced to be of a vivid green hue, but in pouring off the supernatant liquid, and transferring the precipitate upon white paper, it assumed a blue colour, without the least tinge of green; the explanation of the phenomenon, and the fallacy to which it gave rise, was obvious: the yellow colour, imparted to the liquid by the alkali, was the effect of that body upon vegetable extract, and will generally take place on adding it to the infusions of vegetable substances.