4353. Roll Sulphur

4353.    Roll Sulphur. Crude sulphur, purified by melting and skimming it, is poured into cylindrical moulds. Common roll sulphur frequently contains from 3 to 7 per cent, of yellow arsenic.

4354. Sublimed Sulphur

4354.     Sublimed Sulphur. Sometimes called Flowers of Sulphur. This is prepared by subliming sulphur in iron vessels. For medical purposes it is well washed with water and dried by a gentle heat. (Cooley.) An aqueous solution of pure anhydrous carbonate of soda will dissolve an appreciable quantity of flowers of sulphur, by digesting for 10 hours at 212° Fahr. (Pole.)

4355. Sulphur Vivum

4355.     Sulphur Vivum. Crude native sulphur, or black sulphur, is of a grey or mouse-colored powder. The same names are given to the residuum in the subliming pots, after the preparation of flowers of sulphur; it generally contains arsenic.

4356. Tersulphuret of Arsenic

4356.    Tersulphuret of Arsenic. The tersulphuret or tersulphide of arsenic is a fine golden yellow substance in lumps or powder. It is found, ready formed, in nature, or is prepared artificially by sublimation from arsenious acid and sulphur. The artificial sul-phuret, King's Yellow, often contains 80 to 90 per cent, of white arsenic.

4357. Camphor

4357.    Camphor. The camphor of commerce is a natural production. It is principally extracted from the laurel camphor tree, but it is also found in several other members of the vegetable kingdom. It is a white, semi-crystalline solid, very volatile at common temperatures; soluble in alcohol, ether, oils, and acetic acid, and slightly but sufficiently so in water to impart its characteristic smell and taste. The Chinese and Japanese extract the camphor by cutting the wood into small pieces, and boiling it with water in iron vessels - which are covered with large earthen capitals or domes - lined with rice straw. As the water boils, the camphor is volatilized along with the steam, and condenses on the straw, under the form of greyish granulations. In this state it is collected and transported to Europe, when it undergoes the process of refining into white camphor. To refine it, 100 parts of crude camphor are mixed with 2 parts each of quicklime and animal charcoal, and placed in a thin globular glass vessel sunk in a sand-bath. The heat is then cautiously applied, and the vessel gradually and carefully raised out of the sand as the sublimation goes on. When this is completed, the whole is allowed to cool. If the process be conducted too slowly, or at a heat under 375° Fahr., the product will be flaky, and consequently unsaleable, without remelting or subliming.

4358. To Pulverize Camphor

4358.    To Pulverize Camphor. Camphor may be beaten in a mortar for some time, without being reduced to powder, but if it be first broken with the pestle, and then sprinkled with a few drops of spirit of wine, it may be readily pulverized. By adding water to an alcoholic or ethereal solution of camphor, it is precipitated under the form of an impalpable powder of exquisite whiteness, which may be collected and spontaneously dried on a filter; the addition of a minute quantity of carbonate of magnesia to the water (say 1 drachm for each 16 ounces of camphor), before mixing it with the camphor solution, will prevent the powdered camphor from hardening again after drying.