(Acidum Arsenosum. U. S. P., 1890.)

Origin. - Arsenic has been found in minute proportions in many mineral waters. It is obtained in large quantities by roasting arsenical ores - cobalt, nickel, tin, and particularly arsenical iron pyrites - and purifying by resublimation. It should contain not less than 99.8 per cent. of pure arsenic trioxide.

Description and Properties. - It is a heavy solid, occurring either as an opaque white powder or in irregular masses, of two varieties - the one, amorphous, transparent, and colorless, like glass; the other, crystalline, opaque, or white, resembling porcelain. Frequently the glassy variety is found enclosed in an opaque, white crust. Contact with moist air changes the glassy into the white, opaque variety. Both are odorless and tasteless.

Both varieties dissolve very slowly in cold water, the glassy variety requiring about 30, the porcelain-like about 100, parts of water at 250 C. (770 F.). Both are slowly but completely soluble in 15 parts of boiling water. Arsenous acid is but slightly soluble in alcohol, but is soluble in about 5 parts of glycerin. Oil of turpentine dissolves the glassy variety only. Both varieties are freely soluble in hydrochloric acid and in solutions of alkali hydrates and carbonates.

Dose. - 1/60-1/20 grain (0.001-0.003 Gm.) [1/50 grain (0.002 Gm.), U. S. P.].

Official Preparations

Liquor Acidi Arsenosi - Liquoris Acidi Arsenosi - Solution of Arsenous Acid. - Strength, 1 per cent. of arsenic trioxide.

Description and Properties. - A clear, colorless liquid, odorless, having an acidulous taste and an acid reaction.

Dose. - 2-10 minims (0.12-0.6 Cc.) [3 minims (0.2 Cc), U. S. P.].

Liquor Potassii Arsenitis - Liquoris Potassii Arsenitis - Solution of Potassium Arsenite (Fowler's Solution). - Strength, 1 per cent. of arsenic trioxide.

Dose. - 2-10 minims (0.12-0.6 Cc.) [3 minims (0.2 Cc), U. S. P.].