Symptoms, &c.—The symptoms and post-mortem signs have been already described, [p. 246].
Chemical Analysis and Tests.—The acid will have to be examined under the following heads: (1) Simple, concentrated acid. (2) Dilute acid. (3) Mixed with organic liquids, food, vomit, &c. (4) On the clothes of the person injured.
I. Concentrated Acid
1. Chars Organic Matter.—A piece of wood or paper placed in the strong acid rapidly becomes blackened.
2. Heat when added to Water.—Equal quantities of acid and water added together produce intense heat.
3. Evolution of Sulphurous Acid.—When boiled with chips of wood, copper cuttings, or mercury, fumes of sulphurous acid are evolved, detected by their sulphur-like odour, and by their power of first bluing and then bleaching starched paper dipped in iodic acid.
II. Dilute Acid
1. Chars Paper.—This only occurs when the paper is dried by the aid of heat, subsequently to moistening it in the dilute acid.
2. Precipitation of Sulphate of Barium.—A solution of the nitrate or of the chloride of barium is precipitated by sulphuric acid in the form of a white insoluble powder, unaffected by nitric or hydrochloric acid, even when heat is applied. This test is so delicate, that a liquid containing ¹/₂₅₀₀₀th part by weight of the acid is precipitated by either of the test solutions.
3. Action of Heat.—The dilute acid is entirely volatilised by heat.