Source. - Sodae Biboras, by the action of sulphuric acid.

Characters. - In white glittering plates, odourless, with a slightly bitter taste. A weak acid. Solubility, 1 in 26 of cold water, 1 in 3 of hot water; freely in glycerine; less freely in spirit.

Dose. - 5 to 30 gr.

Preparations.

1. "Boracic Lint." Lint steeped in a boiling saturated solution, and dried. Contains nearly half its weight of the acid.

2. Various Ointments and Lotions.

Action And Uses

Externally, boracic acid destroys low organisms, a solution of 1 in 133 arresting the activity of bacteria, and it is thus an anti-septic, disinfectant, and deodorant. On the tissues it produces little or no irritation, and is thus peculiarly adapted for use as a surgical dressing. The lint is now extensively employed in the antiseptic system; and lotions, warm fomentations made from a boiling saturated solution, and ointments with paraffin and vaseline, have almost replaced for the time other applica-tions to wounds and ulcers. As its action does not extend beyond the surface to which it is applied, boric acid is never used for dressing cavities. It relieves itching, in the form of a powder, ointment, or glycerine. It is a test for Rheum (q.v.).

Internally, boric acid is a gastro-intestmal irritant in large doses.

Acidum Sulphurosum, - Sulphurous Acid. Sul-phurous acid gas, SO2, dissolved in water, and constituting 9.2 per cent, by weight of the solution (rarely contains more than 6 per cent).

Source. -Made by heating sulphuric acid with charcoal, and dissolving the gas in water. 4H1SO4 + C2 = 4SO2 + 2CO2 + 4H1O.

Characters. - A colourless liquid, with a pungent sulphurous odour.

Impurities. - Sulphuric acid; mineral matters; excess of water, detected by volumetric starch and iodine test.

Dose. - 1/2 to 1 fl.dr.

Non-officinal Preparations containing Sulphurous Acid.

Sodae Sulphis. - Sulphite of Soda. Na2SO3,7H1O. Source. - Made by saturating a solution of carbonate of soda with sulphurous acid gas.

Characters. - White efflorescent prisms, with a sulphurous taste; feebly alkaline. Soluble in 4 parts of water. Dose. - 5 to 20 gr.