Sulphur, an elementary substance belonging to the class of metalloids. It has been known from the earliest times as the sublimed product of volcanoes, and as a natural mineral deposit in clay and marl strata in tertiary formations, and is also associated with gypsum, being one of the sources of this mineral. (See Gypsum).

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, Mexico. 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 sulphates 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 (Epsom and Glauber's salts). It is a constituent of the proteine compounds of animals and vegetables, in the taurine of bile and the cystine of urine, and certain volatile oils, as oil of onions and oil of mustard. - Sulphur is obtained from the natural deposits of free sulphur by melting or by distillation.

Rich deposits are simply melted in large cast-iron or earthen caldrons, the ganguo and small stones being removed with perforated ladles. Sometimes 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 distillation, 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 furnace 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 vessels, 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.

Sulphur is also a by-product of gas manufacture when salts of iron are used to decompose sulphuretted hydrogen. (See Gas, vol. vii., p. 637.) The iron salt, which before using is mixed with lime and exposed to the air to convert it into peroxide, in the gas-purifying process 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. Sublimed 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 blue flame and emitting suffocating fumes of sulphurous 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, forming respectively chlorides, bromides, and iodides of sulphur. It combines readily with most of the metals, forming sulphides or sulphurets, which generally have a constitution corresponding 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 being soluble and thoso in the second insoluble in bisulphide of carbon. Berthelot has named the first or soluble variety electro-positive sulphur, because it is separated at the positive electrode of a galvanic battery during the electrolysis 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 electronegative sulphur, because it appears at the negative pole of the battery during the decomposition of sulphurous acid, and separates from sulphur compounds with electro-negative elements, as chlorine, bromine, iodine, and oxygen. 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 rhombic base, and all the modifications of both varieties 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 brownish 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 arc not only very unlike as to their crystal-lography, but differ widely in their specific gravities and in their melting points, the octahedral crystals having a density of 2.05 and melting at 239° F., while the needles have a density of only 1.98, that of ordinary roll sulphur, and melt at 248°. After a time the prismatic crystals will be found to consist of aggregations of minute octahedral crystals.

When a saturated solution of sulphur in hot turpentine cools, the first crystals formed will be prismatic, while those which are deposited when the solution is comparatively cool will be octahedrons. Roll sulphur or brimstone is at first prismatic, but after keeping becomes octahedral, and the change of form is attended with the evolution of heat. The amorphous variety of soluble sulphur is precipitated as a greenish white emulsion on adding acids to dilute solutions of alkaline polysulphides. This amorphous sulphur changes after a time into a mass of octahedral crystals. Ordinary sublimed sulphur (flowers of sulphur) belongs to this variety, but always contains small quantities of one of the insoluble modifications. The principal modifications of the insoluble variety of sulphur are : 1, an amorphous modification, obtained as a soft pasty mass, or magma, by decomposing bisulphide of chlorine with water, or by adding dilute hydrochloric acid to a solution of a hyposulphite; 2, a plastic form, obtained by pouring viscid sulphur raised to nearly 500° into cold water. The effect of heat upon sulphur is remarkable. It begins to melt at about 239°, and between 248° and 284° it is yellow, transparent, and limpid.

As the temperature rises to 356° it becomes brown, and at last nearly black and opaque and quite viscid. At this point the temperature becomes stationary for a time, although the supply of heat is kept up, in consequence of a molecular change which is going on. Soon the temperature again rises, and when it has reached about 500° the mass becomes more liquid, but retains considerable viscosity. If it is now suddenly cooled by pouring it in a small stream into cold water, a brown tenacious mass is produced, which may be drawn out into elastic threads having a specific gravity of only 1.957. In a few hours it becomes yellow and opaque, and passes into the octahedral form. If the ductile sulphur is heated to 212°, the change is sudden, with a further rise of heat, from condensation, to 230°. - Compounds. Sulphur forms with oxygen an interesting series of compounds: two anhydrous oxides, or anhydrides, sulphurous anhydride, S02, and sulphuric anhydride, S03; two acids, sulphurous and sulphuric, formed by the union of these anhydrides respectively with water, and a further series of acids which have no corresponding anhydrides. The constitution of all these bodies is remarkably illustrative of the law of multiple proportions.

The formulas of the acids are as follows :

Thiosulphuric acid (Gr. θείον, sulphur) is so called because it has the constitution of sulphuric acid with a molecule of oxygen replaced by one of sulphur. The last four acids in the table are called polythionic acids, because they contain varying proportions of sulphur united with constant proportions of the other elements. Sulphurous anhydride, S02, formerly called sulphurous acid, is the only product when sulphur is burned in dry air or oxygen gas. When the combustion takes place in pure oxygen, it is found that on returning to its former temperature the gaseous product is doubled in weight, but that its volume is unchanged. It is in fact formed by the condensation of one volume of oxygen and half a volume of sulphur vapor into one volume. When required pure, sulphurous acid is usually obtained by the partial reduction of sulphuric acid. This is conveniently effected by boiling strong oil of vitriol with copper turnings or mercury. The reaction is shown in the following equation: Cu + 2H2S04 = CuSo4 + 2H20 + S02. It may also be obtained by passing the vapor of sulphuric acid over red-hot platinum foil or sponge, the product being sulphurous anhydride and oxygen. (See Oxygen, vol. xii., p. 769.) Sulphurous anhydride is a colorless gas, having a density of 2.21. When subjected to a pressure of three atmospheres at common temperatures, or if cooled to 0° F. at the ordinary pressure, it is condensed to a colorless, transparent liquid, which solidifies to a crystalline mass at - 105°. The liquid anhydride may be obtained in large quantities by passing the gas from the generator first through a small quantity of water to wash it, then through a tube surrounded by ice to remove moisture, then through a tube containing pieces of calcium chloride to dry it completely, and finally through a worm, or into a receiver immersed in a mixture of salt and ice.

It may be preserved in sealed glass tubes, or corked and wired soda bottles. Sulphurous anhydride dissolves in water, forming a solution of sulphurous acid, H2S03, which again decomposes by the application of gentle heat into the anhydride and water. Water at 60° absorbs about 45 times its volume of the gas, the resulting liquid having a density of 1.04. By exposure to the air the solution slowly passes into sulphuric acid. By cooling a saturated aqueous solution to 32°, Dopping obtained the pure acid, H2S03, in cubical crystals. A crystalline hydrate, S028H20, according to Pierre, may also be obtained at a low temperature, which melts at 39°, suffering decomposition. Sulphurous acid is a powerful reducing agent, instantly discoloring acid solutions of manganates and chromates, reducing the latter to green oxides of chromium. It reduces the salts of gold, precipitating the metal in the metallic state, and is capable of taking the second molecule of oxygen from almost any metallic binoxide. Brewers often employ a solution of sulphurous acid to wash out their beer barrels, and in the rural districts sulphur is often burned in old cider barrels to purify them.

Sulphurous acid is extensively used in bleaching straw, woollen, and silken goods, and also isinglass and other articles which would be injured by chlorine. (See Bleaching.) It is a powerful antiseptic, and is now employed to preserve meats. (See Preservation of Food, vol. xiii., p. 824.) For its most important use, see Sulphuric Acid. Sulphurous acid is dibasic, forming normal, neutral, and double salts. (See Sulphites.) The binary compounds of sulphur with the metals, or the sulphides, are, when important, mentioned in the articles on the respective metals, or under Sulphides. One of the principal uses of sulphur is in making gunpowder. (See Gunpowder.) - Medical Properties and Uses. Sulphur is termed in therapeutics a laxative, diaphoretic, and alterative. It is supposed to be carried into the circulation by the fatty matters in the alimentary canal. That it is discharged by the skin is shown by the fact that silver worn about those who are taking it becomes blackened with a coating of sulphide.

It is used in cutaneous and other diseases, both internally and externally, sometimes artificially prepared, and sometimes as it exists in natural springs. (See Mineral Springs. ) It has been successfully employed in diphtheritic croup, given suspended in water, and in sciatica and chronic articular rheumatism, applied externally upon dry flannel and bandaged to the limb for several days. The officinal preparations embrace confections, plasters, and ointments, and precipitated sulphur or lac sulphuris. This latter preparation is made by boiling sulphur with milk of lime, which forms bisulphide of calcium and hyposulphite of lime, from the solutions of both of which the sulphur is precipitated by the action of hydrochloric acid. It has the general properties of ordinary sublimed sulphur, but is in a state of finer division.