480 MEDICAL JURISPRUDENCE With a neutral solution of tartaric acid silver nitrate produces a white precipitate of silver tartrate, which dissolves in dilute ammonium hydroxide and forms a beautiful mirror of metallic silver on the sides of the test tubes, when heated on a water bath. CITRIC ACID, CcH8O7) H2O This acid is found free in the juice of lemons, oranges and many other sour fruits, and is stated to occur to the extent of from 0.05 to 0.1 per cent in human and cow's milk. It is prepared by boiling lemon juice and neutralizing with calcium carbonate. It occurs as large, colourless prismatic crystals or as a white powder. It is odourless and strongly acid in taste. It dissolves in less than 1 part of water, in about 1.5 parts of alcohol and is slightly soluble in ether. The pharmacopoeial dose is 5 to 30 grains. As shown by experiments on animals, citric acid is more poisonous than tartaric acid. Fatal cases of poisoning by this acid have occurred. A young girl59 died after she had taken 25 grammes of citric acid as an abortifacient. The treatment is the same as in poisoning by tartaric acid. Tests.—-Calcium chloride yields a white precipitate on boiling but not in the cold. Boiling has no effect on citrates, but potassium permanganate turns them green. It gives no mirror test with silver nitrate. HI ALKALIES Like acids, alkalies act as corrosive poisons when administered in the concentrated form, but act as irritant poisons when diluted. The hydroxides or hydrates and carbonates of alkalies which act as corrosives are the following : — 0 1. Ammonia (Hartshorn), NH$.—Gaseous ammonia, when dissolved in water, forms a strong solution of ammonia (Liquor Ammonias Fortis), known as spirits of Hartshorn. It contains 32.5 per cent of ammonia and is a colourless1 liquid, having a very pungent characteristic odour, and a strong alkaline reaction. The solution is largely employed for domestic purposes, such as removing paint, oil, and dirt generally from clothing. The pharma- copoeial preparation, liquor ammonise dilutus (liquor ammoniae) is an aqueous solution containing 10 per cent of ammonia by weight. 2. Potassium Hydroxide (Potassium Hydrate, Caustic Potash), KOH.— " This is usually met with as hard, deliquescent, white pencils or cakes, It is soapy to the touch, acrid to the taste, rapidly absorbs carbon dioxide from the air, and is very soluble in water. Its solution is known as liquor potassae (liquor potassii hydroxidi), which has also a soapy feel, and a strong alkaline reaction, and contains 5 per cent of caustic potash in water. 3. Sodium Hydroxide (Sodium Hydrate, Caustic Soda), NaOH.—This occurs as white, solid masses or as cylindrical stacks, closely resembling potassium hydroxide. It is strongly caustic and, when dissolved in water, forms a solution known as liquor sodise. It is largely employed in manu- factures, but cases of poisoning are rarely met with. 4. Ammonium Carbonate (Sal Volatile), (NH4)2 CO3.—This occurs as translucent, hard, crystalline masses. It has a strongly ammoniacal odour and a pungent, ammoniacal taste. It is soluble in 4 parts of water. Ebcposed to the air it partially dissociates, and becomes converted into porous lumps or a white powder. Commercial ammonium carbonate is a mixture of hydrogen ammonium carbonate and ammonium carbonate, and possesses a strongly ammoniacal odour. 5. Potassium Carbonate (Pearl Ash, Salt of Tartar, Javakhar), KsCOs- —This salt occurs as a white, crystalline powder, having a caustic and alkaline taste. It is highly deliquescent, and very soluble in water but insoluble in alcohol. It is used for washing and other cleansing purposes, 59. Zangger quoted in Erich Leschke, Clinical Toxicology, Eng, Transl., by Stewart and Dorrer, 1934, p. 270.