Page:The British pharmacopœia.djvu/511

Rh Dissolve the oxalic acid in, the water, neutralise the solution with the carbonate of ammonium at, finally, a boiling temperature; filter it while still hot, and set it by that crystals may form as it cools.

PETROLEUM SPIRIT.

Synonyms.—Benzollne; Petroleum Ether.

A colourless very volatile and highly inflammable liquid obtained from petroleum, and consisting of a mixture of the lower members of the paraffin or marsh-gas series of hydrocarbons. Boiling point 122° to 140° F. (50° to 60° C). Specific gravity about 0.670 to 0.700.

PHENOL-PHTHALEIN.

Produced by reaction of phenol and phthalic anhydride. Its tincture yields an intense red colour with potash or soda, hence may be used as an indicator of the termination of volumetric reactions, especially those with organic acids.

PLATINUM BLACK.

Platinum in a state of minute division, obtained by adding excess of carbonate of sodium and some sugar to solution of perchloride of platmum, and boiling until a black precipitate is formed, which is washed and dried.

PLATINUM FOIL.

SUBACETATE OF COPPER OF COMMERCE.

Verdigris.

SULPHATE OF COPPER, ANHYDROUS.

CuSO4.

Sulphate of copper deprived of its water by a temperature of 400° F. (204°.4 C.)

Characters—A yellowish-white powder, which becomes blue when moistened with water.