The _post-mortem_ appearances are inflammation and softening of the mucous membrane of the mouth, gullet, and stomach, which may also be covered with chocolate-coloured or black spots. When life has been prolonged for some months the stomach may become contracted, the pyloric orifice scarcely admitting the passage of a fine probe. _Chemical Analysis._--The caustic alkalies are known from their carbonates by giving a brown precipitate with nitrate of silver; whereas their carbonates give a white, and also effervesce on the addition of an acid. The following table will show the reaction of these alkalies with reagents: To distinguish Caustic Potash from Caustic Soda +--------------------+--------------------------+-----------------+ | | Potash. | Soda. | +--------------------+--------------------------+-----------------+ | Bichloride of | A canary-coloured | No precipitate. | | platinum. | precipitate | | | | in solutions | | | | acidulated with | | | | hydrochloric acid. | | | | | | | Strong solution of | Precipitate in granular | No precipitate. | | tartaric acid. | white crystals. | | | | | | | Colour given to | Rose or lilac tint. | Yellow tint. | | flame. | | | | | | | | Neutralised with | Crystallises in long, | Crystallises in | | nitric acid. | slender, fluted prisms.| rhombic plates.| +--------------------+--------------------------+-----------------+ _In Organic Mixtures._--If the mixture be strongly alkaline, filter and test as above. _Fatal Period._--From three hours to as many years. _Fatal Dose._--About half an ounce of the caustic alkali. The smallest fatal dose recorded of caustic potash is forty grains. _Treatment._--Water freely; drinks containing citric or acetic acid, vinegar, lemon juice, oil, linseed tea, and other demulcent drinks. The stomach tube should be avoided. AMMONIA In vapour, in solution, or solid.