Organic Lesions discovered on Dissection.
The œsophagus and stomach will be found inflamed, and sometimes eroded, as in poisoning by arsenic. Salin has asserted, that this salt never produces perforation of the intestinal tube; this, however, is not the fact; and we know not of any exclusive appearances, by which the organic lesions inflicted by this poison can be distinguished, unless indeed it be the black appearance of the stomach, as if it had been burnt, which occasionally presents itself.
Of the Chemical Processes by which the presence of Corrosive Sublimate may be detected.
As the chemist, devoted to forensic enquiry, will be required to identify this substance under very different states of mixture and combination, we shall proceed to enumerate the various obstacles that may possibly oppose his researches; and, at the same time, to suggest the expedients by which they may be successfully evaded. Unlike arsenious acid, corrosive sublimate is so readily decomposed by various alimentary substances, that, when we attempt to demonstrate its presence in such mixtures, we shall be more frequently compelled to rest our proof upon the products of the analysis, than upon the actual reproduction of the salt.
We shall proceed to consider the best modes of establishing the presence of this salt, in the different forms in which it may occur, viz. 1, In the solid form; 2, Dissolved in water or spirit; 3, In various coloured liquids; 4, In a state of mixture with various solids; 5, Combined with solid or liquid aliments, by which it undergoes decomposition; 6, In a state of combination with the textures of the alimentary canal.
1. The sublimate is in its solid form. The external characters by which this salt is distinguished will go far to establish its identity; but the fact should always receive the support of a chemical proof; and as this is to be derived from the phenomena afforded by its solutions through the intervention of various tests, it will meet with full consideration in the following section, viz.
2. The salt is in the state of solution, in water, or spirit. Let us then suppose that we have a solution of some body in distilled water, which we suspect to be corrosive sublimate, by what means are we able to identify it?
(a) By its metallization, through the agency of galvanism. We are indebted to Mr. Sylvester for first suggesting the mode by which galvanic electricity might be applied for the detection of minute quantities of corrosive sublimate in solution. His method is as follows. A piece of zinc or iron wire, about three inches in length, is to be twice bent at right angles, so as to resemble the greek letter π, the two legs of this figure should be distant about the diameter of a common wedding ring from each other, and the two ends of the bent wire must afterwards be tied to a ring of this description. Let a plate of glass, not less than three inches square, be laid as nearly horizontal as possible, and on one side drop some sulphuric acid, diluted with about six times its weight of water, till it spreads to the size of a halfpenny. At a little distance from this, towards the other side, next drop some of the solution supposed to contain corrosive sublimate, till the edges of the two liquids become joined; and let the wire and ring, prepared as above, be laid in such a way, that the wire may touch the acid, while the gold ring is in contact with the suspected liquid. If the minutest quantity of corrosive sublimate be present, the ring, in a few minutes, will be covered with metallic mercury on the part which touched the fluid.
The above experiment may be beautifully simplified in the following manner[[282]]. Drop a small quantity of a solution, supposed to contain the salt in question, on a piece of gold, and bring into contact a key, or some piece of iron, so as to form a galvanic circuit; when, if sublimate be present, the gold will immediately be whitened.
A solution of nitrate of silver will, under similar treatment, occasion on gold a white precipitate; but as no amalgamation takes place, it is readily wiped off, and cannot therefore occasion any fallacy.