It contains 96.8 per cent. of H2SO4 (98) and corresponds to 79 per cent. of anhydrous sulphuric acid, SO3 (80).

Properties. - A colourless, oily-looking, heavy liquid. Sp. gr-1.843; no smell, but intensely acid taste. It blackens and corrodes most organic substances. It has a great affinity for water, and when mixed with it evolves much heat. When diluted it gives a copious white precipitate of barium sulphate (BaS04) with chloride of barium, insoluble in nitric or in hydrochloric acid.

Preparation. - Vide p. 565.

Impurities. - Lead derived from the leaden chambers in which it is prepared; nitric acid from the nitrous fumes; arsenic from impure sulphur being used and the arsenious fumes passing over with the sulphurous acid; and water from imperfect concentration or fraudulent addition.

Tests. - Not unfrequently it contains so much lead in the form of sulphate that when diluted with water it deposits a white precipitate, the sulphate being soluble in the strong but not in the weak acid. It should not do this, and when evaporated in a platinum dish it should leave little or no residue (no lead, arsenic, or saline impurities). When a solution of sulphate of iron is carefully poured over its surface there is no purple colour developed where the two liquids unite (no nitric acid). Diluted with six times its volume of distilled water it gives no precipitate with sulphuretted hydrogen (no arsenic or lead). The absence of water is ascertained by the sp. gr. not being below 1.840, and by the volumetric estimation of its neutralising power with solution of soda.

Officinal Preparations

B.P.

U.S.P.

Acidum Sulphuricum Aromaticum.

Acidum Sulphuricum Aromaticum.

„ „ Dilutum.

,, ,, Dilutum.

Infusum Rosae Acidum.

Acidum Sulphuricum Aromaticum, B. and U.S.P. Aromatic Sulphuric Acid. Is sulphuric acid diluted with alcohol and flavoured with cinnamon and ginger. About 1 in 13 B.P., and 1 in 10 U.S.P. by measure.

Infusum Cinchonae Acidum contains aromatic sulphuric acid 1 part in 80.

Acidum Sulphuricum Dilutum, B. and U.S.P. Dilute Sulphuric Acid. Is the strong acid diluted with 11 parts B.P., 16 1/2 parts U.S.P., of water by measure; 1 in 10 by weight U.S.P.

Doses. - Of either aromatic or dilute sulphuric acid 5-30 min. freely diluted.

Incompatibles. - Preparations of lead.

Action. - It is a most powerful caustic, and quickly chars and destroys the parts it touches. When mixed with charcoal paste it is used as a caustic in cancer, and with lard in obstinate skin-diseases. When swallowed, as it not unfrequently is in manufacturing districts, it produces symptoms of irritant poisoning (p. 395). The antidotes are alkalis, soap, oil, whiting, milk, plaster from the wall, or magnesia.

Uses. - Internally it is used, after free dilution, to quench thirst in fever, to prevent absorption of lead from the stomach in painters and colour-grinders, to check diarrhoea, especially in phthisis, to arrest haemoptysis and other haemorrhages, and to lessen night-sweats and mucous discharges.