Nitric Acid, or aqua fortis, is less frequently used as a poison than sulphuric acid. The fumes from nitric acid have caused death from pneumonia in ten or twelve hours.

Method of Extraction from the Stomach.—The same as for sulphuric acid. In beer, etc., the mixture may be neutralized with carbonate of potassium, dialyzed, the fluid concentrated and allowed to crystallize, when crystals of nitrate of potassium may be recognized.

Post-Mortem Appearance.—The mucous membranes are rendered yellow or greenish if bile be present; they are also thickened and hardened.

Tests.—Concentrated acid gives off irritating orange-coloured fumes of nitric acid gas. When poured on copper, it gives off red fumes and leaves a green solution of nitrate of copper. It gives a red colour with brucine, turns the green sulphate of iron black, and with hydrochloric acid dissolves gold. A delicate test for the acid, free or in combination, is to dissolve in the suspected fluid some crystals of ferrous sulphate, and then to gently pour down the test-tube some strong sulphuric acid. Where the two liquids meet, if nitric acid be present, a reddish-brown ring will be formed. It turns the skin bright yellow, and does the same with woollen clothes, from the formation of picric acid.

Fatal Dose.—Two drachms.

Fatal Period.—Shortest, one hour and three-quarters in an adult; in infants in a few minutes, from suffocation.