456 SULPHUR It occurs in some schistose rocks, and in coal and lignite deposits, and is deposited from the sulphuretted waters of certain mineral springs. It is found in Sicily in beds of blue clay lying in a matrix of rock salt, gypsum, and celestine. (See STRONTIUM.) It also exists in primitive rocks, as granite and mica, and abounds in the lava fissures of volcanic craters, as in the sol- fatara near Naples and at Popocatepetl, Mexi- co. It is a constituent of many minerals, such as iron and copper pyrites, galena or sulphuret of lead, cinnabar or sulphuret of mercury, gray antimony, and realgar or sulphuret of arsenic; also of ternary salts of metals, such as the sul- phates of copper and iron, and of strontia, barium, and calcium (celestine, heavy spar, and gypsum) ; and of more soluble compounds which are constituents of mineral waters, as the sulphates of magnesium and sodium (Ep- som and Glauber's salts). It is a constituent of the proteine compounds of animals and vegetables, in the taurine of bile and the cys- tine of urine, and certain volatile oils, as oil of onions and oil of mustard. Sulphur is ob- tained from the natural deposits of free sul- phur by melting or by distillation. Rich de- posits are simply melted in large cast-iron or earthen caldrons, the gangue and small stones being removed with perforated ladles. Some- times rude furnaces somewhat like lime kilns are employed for the coarser deposits, in which a portion of the sulphur is burned, while the great mass is drawn off at the bottom. A better method than the latter is that of dis- tillation, as the product is much purer. This is done in large earthen pots or retorts placed in a long furnace. Rude receivers of earthen- ware or wood are placed outside of the fur- nace in which the sublimate is condensed. The product obtained by melting is known as rough sulphur, and contains about 3 per cent, of foreign matter, from which it is separated by distillation, in stills having large chambers for condensers, in which it is deposited in the form known as flowers of sulphur; or it may be condensed in the liquid form in smaller and hotter receivers, and cast into cylinders called roll sulphur. Sulphur may also be obtained from iron pyrites by heating it in close ves- sels, in which case the dioxide parts with one molecule of sulphur and becomes protoxide. It is one of the products of the heating of copper pyrites preliminary to copper smelting. Sul- phur is also a by-product of gas manufacture when salts of iron are used to decompose sul- phuretted hydrogen. (See GAS, vol. vii., p. 637.) The iron salt, which before using is mixed with lime and exposed to the air to con- vert it into peroxide, in the gas-purifying pro- cess becomes a hydrated sulphide. This is again reconverted into peroxide by exposure to the air, with evolution of sulphur. Properties. Native sulphur occurs either in amorphous masses, or in transparent yellow crystals derived from the octahedron with a rhombic base. Sub- limed sulphur of commerce, known as flowers of sulphur, is a yellow gritty powder having a slight peculiar odor, but from its insolubility is nearly tasteless. It is a non-conductor of electricity, and becomes negatively excited on being rubbed by most substances. It has a strong affinity for oxygen, taking fire when heated in the air to 455, burning with a bine flame and emitting suffocating fumes of sul- phurous anhydride. It is therefore classed among highly inflammable substances. It melts at 239, forming an amber-yellow liquid which is lighter than solid sulphur. It boils at about 836, forming a deep yellow vapor of sp. gr. 6-617, one volume of which contains three atoms of sulphur. When heated to about 1832 the vapor is only one third as dense as at 900, and then has the same atomic volume as oxygen. Sulphur has also a very strong affinity for chlorine, bromine, and iodine, form- ing respectively chlorides, bromides, and iodides of sulphur. It combines readily with most of the metals, forming sulphides or sulphurets, which generally have a constitution correspond- ing to the oxides of the same metals. Sulphur, like phosphorus, is remarkable for the number of modifications or allotropic conditions which it may assume under different circumstances. (See ALLOTROPISM, and PHOSPHORUS.) These different modifications are divided into two distinct varieties, those in the first variety be- ing soluble and those in the second insoluble in bisulphide of carbon. Berthelot has named the first or soluble variety electro-positive sul- phur, because it is separated at the positive electrode of a galvanic battery during the elec- trolysis of a solution of hydrosulphuric acid, and also because it is in this form that it is separated from sulphides of electro-positive metals. The second variety he named electro- negative sulphur, because it appears at the negative pole of the battery during the decom- position of sulphurous acid, and separates from sulphur compounds with electro-negative ele- ments, as chlorine, bromine, iodine, and oxy- gen. Soluble sulphur, or that which is soluble in bisulphide of carbon, presents three forms, two crystalline and one amorphous. In the first the crystals are octahedrons with a rhom- bic base, and all the modifications of both vari- eties have a tendency finally to assume this form. It is formed when sulphur separates from its solutions at common temperatures. The second crystalline form is that of brown- ish yellow needles belonging to the oblique prismatic system. It is obtained by melting a mass of sulphur, allowing it to solidify on the surface, piercing the crust, and allowing the fluid portion to run out. On breaking away a part of the crust the long, needle-like crystals will be exposed to view. These two forms are not only very unlike as to their crystal- lography, but differ widely in their specific gravities and in their melting points, the octa- hedral crystals having a density of 2'05 and melting at 239 F., while the needles have a density of only T98, that of ordinary roll sul-
