This substance is one of the products of the distillation of petroleum, coal, peat, and other carbonaceous sources. It is a crystalline, brittle body, closely resembling wax in appearance and melting between 51 and 60° C. (124 and 140° F.). Paraffin, which is now made on a large scale for the manufacture of candles, is very useful in perfumery as a partial substitute for the much more expensive wax or spermaceti, over which it has the advantage, besides its cheapness, that it imparts to the articles great transparency—a quality which is valued highly in fine perfumeries. The addition of some paraffin to pomades renders them more consistent and counteracts their tendency to become rancid. Distilled paraffin always has a crystalline form, differing from the paraffin-like residues left after the distillation of petroleum (so-called vaselins, etc., see below) which are always amorphous. PYROGALLIC ACID appears in commerce as a white crystalline powder, made by heating gallic acid to 200-210° C. (392-410° F.). With iron salts, pyrogallic acid forms bluish-black combinations and precipitates the metal from silver solutions as a velvety-black powder. On account of these properties pyrogallic acid is used in perfumery as a constituent of some hair dyes. SULPHIDE OF POTASSIUM, liver of sulphur, hepar sulphuris, potassii sulphuretum, the pentasulphide of potassium, is obtained by fusing together potash and sulphur, in the shape of a leather-brown mass which is soluble in water and on exposure to the air is gradually decomposed with the development of the offensive sulphuretted hydrogen gas; hence it should be preserved in well-closed vessels. An aqueous solution of this substance forms with lead or silver salts a black precipitate of sulphide of lead or silver, and is used for some hair dyes. STARCH FLOUR (amylum) is prepared from various vegetables such as potatoes, rice, arrowroot, sago, etc., and when pure appears as an insoluble white powder which the microscope shows to be grains consisting of many superimposed layers. In commerce the price of the different varieties of starch fluctuates greatly; in perfumery well-cleansed potato starch can very well be used for dusting powders, and the so-called poudre de riz; in this country, corn starch is preferable. VANILLIN, that is, the body to which vanilla owes its fragrance, is now made artificially and can be used in place of vanilla for soaps and pomades. VASELIN.