case of supposed poisoning with any of the three mineral acids mentioned above, it will be unnecessary to notice any of their chemical properties, except those from which their medico-legal tests are derived.
The only common properties that require notice are, their power of reddening the vegetable blue colours, for showing which litmus-paper is commonly used, and is most convenient: and their power of staining and corroding all articles of dress, especially such as are made of wool, hair, and leather. This last property is specified, though a familiar one, because it always forms important evidence in criminal cases. In order to give precision to such evidence, it is necessary to remember, that if the article of dress is a coloured one, it is generally rendered red by the mineral acids; but that the vegetable acids also will redden most articles of dress, although they do not corrode them.
I.—Of Poisoning with Sulphuric Acid.
Sulphuric acid is extensively employed in very many trades, is used even for some domestic purposes, and is consequently familiar to every one. Hence it is the mineral acid which has been most commonly used as a poison, especially for committing suicide. Of 35 cases of poisoning with the mineral acids which occurred in England in the years 1837 and 1838, 32 were caused by this acid (p. 90).
Section I.—Of the Tests for Sulphuric Acid.
Sulphuric acid is known as a poison chiefly in the form of the concentrated commercial acid. But a few cases of poisoning have also been produced by blue-liquor or the solution of indigo in strong sulphuric acid; and one instance[1] has been recorded of poisoning with the aromatic sulphuric acid of the Pharmacopœias, which is an infusion of aromatics in a mixture of sulphuric acid, ether and alcohol. In the following remarks on its tests, it will be sufficient to consider it first in the concentrated form,—secondly, in a state of simple dilution,—and thirdly, when mixed with various impurities, more especially with vegetable and animal matter. The acid solution of indigo may be known by the tests for the concentrated acid, and its blue colour, removable by a solution of chlorine; and the aromatic sulphuric acid may be distinguished by its odour and the tests for the diluted acid.
1. When concentrated it is oily-looking, colourless, or brownish from having acted on organic particles, without odour, much heavier than water, and capable of quickly corroding animal substances. If from these properties, and its effect in reddening litmus, its exact nature be not considered obvious, it may be heated with a few chips of copper; when sulphurous acid is disengaged and may be readily recognised by its odour.
- ↑ London Med. Gazette, 1839-40, i. 944.
