This occurs as a mineral chiefly in the Upper Miocene deposits and in the Flötz, associated in general with gypsum, massive limestone, and marl. Commercially important deposits are found in Sicily (provinces of Caltanissetta, Girgenti, Catania), Italy (Latera and Scrofano, province of Rome), Spain (Teruel and Arcos), France (dept. Vaucluse), Transylvania, Poland (Swoszowice near Cracow), and Germany (Lüneburg, in Hanover). The exhalations of volcanoes include, as a rule, sulphurous acid, SO 2 , and sulphuretted hydrogen, H 2 S, which two gases, if moist, readily decompose each other into water and sulphur,—a circumstance which accounts for the constant occurrence of sulphur in all volcanic districts. Mt Purace in Colombia wears a cap of sulphur (derived from its own crater) which accumulates at the rate of about 2 feet per annum,— its superficial area amounting to 1435 square yards. The solfatara at Bahara Saphinque on the Red Sea is said to yield 600 tons of sulphur annually. The molten sulphur discharged from the crater of the Alaghez in the Armenian highlands forms solid excrescences, which the natives dislodge from their inaccessible positions by means of rifleshots. A sulphur deposit near the Borax Lake in California is estimated to contain 20,000 tons. Most of the sulphur or brimstone of commerce comes from the rich fields of Sicily, where in 1884 the annual production had almost reached 400,000 tons. The mode of mining there adopted is by a network of horizontal galleries (tunnels) driven through the deposit; the solid squares thus marked off are hewn out, a central pillar being left to support the roof. The total excavation is generally 100 feet high and from 25 to 50 wide; not unfrequently the whole collapses. Down to a comparatively recent date all the work used to be done by hand, boys of eight to ten years of age being employed to carry the ore to the shaft and thence to the surface; only where a mine has reached a depth of 325 feet or more is water-power, if available, resorted to. Since 1868, however, the ore at Grotta Calda at least has been raised by properly constructed shafts with the help of steam-power, and this system is spreading.

The Sicilian ores are customarily classified as follows :—

Per 100 parts of ore Per 100 parts of ore

Sulphur present. Sulphur recovered.

Richest ores .... 30-40 20-25

Rich ores 25-30 15-20

Ordinary 20-25 10-15

The poor yield of actual sulphur is explained by the rather primitive method used for its extraction. A semicircular or semi-elliptical pit (calcarone) about 33 feet in diameter and 8 deep is dug into the slope of a hill, and the sides are coated with a wall of stone. The sole consists of two halves slanting against each other, the line of intersection forming a descending gutter which runs to the outlet. This outlet having been closed by small stones and sulphate of lime cement, the pit is filled with sulphur ore, whieh is heaped up considerably beyond the edge of the pit and covered with a layer of burnt-out ore. In building up the heap a number of narrow vertical passages are left to afford a draught for the fire. The ore is kindled from above and the fire so regulated (by making or unmaking air-holes in the covering) that, by the heat produced by the combustion of the least sufficient quantity of sulphur, the rest is liquefied. The molten sulphur accumulates on the sole, whence it is from time to time run out into a square stone receptacle, from whieh it is ladled into damp poplar-wood moulds and so brought into the shape of truncated cones weighing 110 to 130 lb each. These cakes are sent out into commerce. A calcarone with a capacity of 28,256 cubic feet burns for about two months, and yields about 200 tons of sulphur. The immense volumes of sulphurous acid evolved give lise to many complaints; all the minor pits suspend work during the summer to avoid destruction of the crops. A calcarone that is to be used all the year round must be at least 220 yards from any inhabited place and 110 from any field under cultivation.

The yield of sulphur, as seen from the table given above, is miserably small, but the scarcity of fuel in Sicily almost prohibits the introduction of any more rational method. As sulphur fuses at 114° C., high-pressure steam at once suggests itself as a suitable medium of heating. In the sulphur-works of Latera, in the province of Rome, the following apparatus (constructed by Gritti) is being used with success. A vertical truncated perforated cone of thick sheet-iron serves for the reception of the ore. This cone is enclosed in a similar cone of iron, which terminates in a detachable deep iron basin below, and is provided with a tightly fitting lid. All tho joints in this outer shell are steam-tight. The inner cone having been charged and the lid secured, steam of sufficient pressure to ensure a temperature of from 125° to 135° C. is blown into the apparatus, which soon causes the sulphur to melt and collect in the basin below. After from 30 to 50 minutes, reckoning from the time when the above temperature is reached, the operation is completed. The steam is then turned off and the sulphur made to run from the basin into a receptacle beside the apparatus, to be cast into sticks or cakes. The iron basin is then detached, and by turning aside an iron damper which held the ore in its place the exhausted ore is made to drop into a pit. Each charge of ore amounts to about from 25½ to 26½ cwts., containing about 385 lb of sulphur. Of this some 360 lb are recovered as saleable sulphur, at the expense of about 286 lb of oak-wood as fuel.

R. E. Bollmann in 1867 proposed to extract the sulphur by means of bisulphide of carbon. The process, after having been tried at Bagnoli near Naples and given up as hopeless, was introduced in 1873 in Swoszowice near Cracow under the guidance of Winkler and has proved a success. The apparatus is constructed so that the bisulphide used in the process of extraction is recovered by distillation; the loss of bisulphide amounts only to one-half per cent., sometimes to less, and the sulphur produced is very pure. But by far the greater part of the purer qualities of commercial sulphur is produced from Sicilian calcarone sulphur by distillation, which removes the 3 per cent. or so of earthy impurities contained in it. The following apparatus (invented originally by Michel of Marseilles and improved subsequently by others) enables the manufacturer to produce either of two forms of “refined” sulphur which commerce demands. It consists of a stone-built chamber of about 2825 cubic feet capacity, whieh communicates directly with two slightly slanting tubular retorts of iron, each of which holds about 660 lb of sulphur. The retorts are charged with molten sulphur from an upper reservoir, which is kept at the requisite temperature by means of the lost heat of the retort fires. The chamber has a safety valve at the top of its vault, which is so balanced that the least surplus pressure from within sends it up. The first puff of sulphur vapour which enters the chamber takes fire and converts the air of the chamber into a mixture of nitrogen and sulphurous acid. The next following instalments of vapour, getting diffused throughout a large mass of relatively cold gas, condense into a kind of “snow,” known in commerce and valued as “flowers of sulphur” (flores sulphuris). By conducting the distillation slowly, so that the temperature within the chamber remains at a sufficiently low degree, it is possible to obtain the whole of the product in the form of “flowers.” If compact (“roll ”) sulphur is wanted the distillation is made to go on at the quickest admissible rate. The temperature of the interior of the chamber soon rises to more than the fusing-point of sulphur (114° C. ), and the distillate accumulates at the bottom as a liquid, which is tapped off from time to time to be cast into the customary form of rods of about 1½ inches diameter.

In some places sulphur is extracted from iron pyrites by one of two methods. The pyrites is subjected to dry distillation from out of iron or fire-clay tubular retorts at a bright red heat. One-third of the sulphur is volatilized—3FeS 2 = Fe 3 S 4 + S 2 —and obtained as a distillate. The second method is analogous to the calcarone method of liquation: the ore is placed in a lime-kiln like furnace over a mass of kindled fuel to start a partial combustion of the mineral, and the process is so regulated that, by the heat generated, the unburnt part is decomposed with elimination of sulphur, which collects in the molten state on an inverted roof-shaped sole below the furnace and is thence conducted into a cistern. Such pyrites sulphur is usually contaminated with arsenic, and consequently is of less value than Sicilian sulphur, which is characteristically free from this impurity.

The substance known as “milk of sulphur” {lac sulphuris) is very finely divided sulphur produced by the following, or some analogous, chemical process. One part of quicklime is slaked by means of 6 parts of water, and the paste produced diluted with 24 parts of water; 2·3 parts of flowers of sulphur are added; and the whole is boiled for about an hour or longer, when the sulphur dissolves,—

3CaO + 12S = 2CaS 5 + CaS 2 O 3 ∙

The mixed solution of pentasulphide and thiosulphate of calcium thus produced is clarified, diluted more largely in a tub, and then mixed with enough of pure dilute hydrochloric acid to produce a feebly alkaline mixture; this shows that only the bulk of the pentasulphide is decomposed,—CaS 5 + 2HCl = CaCl 2 + H 2 S + (4S of precipitated sulphur). The addition of more acid would produce an additional supply of sulphur (by the action of the H 2 S 2 O 3 on the dissolved H 2 S); but this thiosulphate sulphur is yellow and compact, while the CaS 5 part has the desired qualities, forming an extremely fine, almost white, powder. The precipitate is washed, collected, and dried at a very moderate heat. It is used as a medicine. If sulphuric acid is used instead of hydrochloric acid the preparation is apt to be contaminated with hydrated sulphate of lime. In the United Kingdom, indeed, precipitated sulphate of lime used to be added intentionally to produce what the public had got accustomed to; but this practice has been rightly stopped by the authorities.

During the year 1875 the production of sulphur in Europe is stated to have been as follows :—

Tons.

Italy 360,000

Spain 4,000

Austria-Hungary 3 750

German empire (including 5000 tons of regenerated sulphur) 14,500 Belgium 450

Total 382,700

By far the greater part of all the sulphur produced in Sicily and elsewhere is used for the manufacture of sulphuric acid. Subjoined is an enumeration of some other applications. (1) The manufacture of gunpowder (see vol. xi. p. 320). (2) The taking of casts. (3)

The making of cements: (a) a mixture of molten sulphur and ferric oxide is used to cement the isolating bells to telegraph posts; {b) a mixture of iron filings (100), flowers of sulphur (3 to 20), and sal-ammoniac (3 to 5) made into paste with water is used to cement iron bars (fences, &c.) into stone sockets; (c ) a mixture of molten sulphur with powdered quartz or glass has been recommended as an acid-proof material for sulphuric acid chambers; {d) a mixture produced by the incorporation of powdered quartz and colouring matters, such as vermilion, &c., with molten sulphur is employed for ornamental articles. (4) The vulcanization of india-rubber (see vol. xii. p. 840 sq.). (5) Dusting vine-plants with flowers of sul phur is said to keep off the fungus Oidium Tuckeri, which has caused such devastation in the vineyards in France and elsewhere.

Sulphur Compounds.

Sulphuretted hydrogen, H 2 S (see Chemistry, vol. v. p. 499 sq.), is used largely as such, or as sulphide of ammonium, (NH 4 ) 2 S = 2NH 3 + H 2 S, for the detection, discrimination, and separation of metals. To give an example: the least quantity of lead dissolved in water as (say) nitrate can be detected by the addition of sulphuretted hydrogen, which brings down the lead as a black precipitate of sulphide of lead,—Pb(NO 3 ) 2 + H 2 S = PbS + 2HNO 3 . The presence of a moderate quantity of mineral acid in the original solution does not interfere with the test. What we said of solution of salts of lead holds substantially of those of the following groups of metals. The formulae and the colours of the sulphides are given in brackets. A. Lead (black, PbS), silver (black, Ag 2 S), mercury as mercurous or mercuric salt (black, HgS + Hg or HgS respectively), copper (greenish black, CuS), bismuth (brown, Bi 2 S 3 ), cadmium (yellow, CdS). B. Arsenic (yellow, As 2 S 3 ), antimony (orange-red, Sb 2 S 3 ), tin as stannic salt (yellow, SnS 2 ). The sulphides A are insoluble; the sulphides B are soluble in sulphide of ammonium solution, and the latter, from this solution, can be reprecipitated by acidification with dilute sulphuric or hydrochloric acid. The brown SnS precipitated from stannous salts is insoluble in the (colourless) solution of (NH 4 ) 2 S, but soluble in the yellow solution of the polysulphide (NH 4 ) 2 S 2 , as SnS 2 . C. The following metals are not precipitated from their salt solutions if these are acidified sufficiently by added mineral acid; but they are precipitated from their neutral or alkaline solutions by sulphide of ammonium :—iron (black, FeS), nickel (black, NiS), cobalt (black, CoS), manganese (flesh-coloured, MnS), zinc (white, ZnS). Aluminium and chromium, given as salts of their oxides, R 2 O 3 , are precipitated by sulphide of ammonium as hydrated oxides (Al 2 O 3 . x H 2 O, colourless; Cr 2 O 3 .H 2 O, green or violet). The reagent acts on these as ammonia, NH 3 , the H 2 S being liberated, and behaves in a similar way to acid solutions of certain salts, e.g., the phosphates, of the following group D, these salts, e.g., Ca 3 P 2 O 8 , being precipitated as such. The ordinary salts of group D (barium, strontium, calcium, magnesium), and the salts of the alkali metals E (potassium, sodium, &c.) generally, give no precipitate with either sulphuretted hydrogen or sulphide of ammonium. It is easy to translate what we have stated into a method for the separation of groups A, B, C (D and E), from one another.

Of the three chlorides treated of in Chemistry (vol. v. p. 501) only the lowest, S 2 Cl 2 , is of industrial importance. It is prepared by passing perfectly dry chlorine gas over heated sulphur contained in a retort, the retort being connected with a condenser constructed so that the uncondensed vapours are led away into the chimney. The two elements unite readily, and chloride of sulphur, S 2 Cl 2 , distils over, contaminated, however, by more or less of surplus chlorine present as higher chlorides. To remove (or decompose) these the crude product is subjected to fractional distillation; the thermometer rises rapidly and soon becomes constant (at about 136 under 758 mm. pressure). What afterwards distils over, at the constant boiling-point, is collected as pure S 2 Cl 2 ,-ayellowish red liquid of 1·68 sp. gr. at 16°·7 C. and 1·7055 at 0° (Kopp), which emits fumes of hydrochloric acid in moist air. Its smell is charac- teristic and unpleasant. Chloride of sulphur is decomposed by water, alcohol, ether (see Chemistry) ; and benzol and bisulphide of carbon mix with it in all proportions without decomposition. A mixture of 100 parts of bisulphide of carbon and some 2·5 of chloride of sulphur is used for the vulcanization of (chiefly sheet) india-rubber. The mixture is readily imbibed by the rubber, which when allowed to dry (at from 22° to 25° C.) gives up the bisulphide of carbon and the chlorine of the reagent, the latter as HC1, but retains its sulphur in a state of chemical combination.

The gas SO 2 (see Chemistry, vol. v. p. 501), produced extempore by the combustion of sulphur, is used for the bleaching of silk, wool, straw, and wicker work, also for the disinfection of rooms and of wine-casks (to prevent acetous fermentation). A solution of the gas in water is manufactured industrially, for use chiefly in the manufacture of sugar. It is added to the beetroot or cane juice to prevent its fermentation while awaiting concentration. A solution of “bisulphite of lime” (produced by saturating milk of lime with sulphurous acid gas) is much used as an antiseptic generally. Liquefied sulphur dioxide has found an application as a frigorific for the manufacture of ice. The apparatus used is so constructed that the volatilized sulphur dioxide is all caught and recondensed. Sulphurous acid when required as such or for the making of sulphites is always produced, even industrially, from oil of vitriol, by reduction with either sulphur or charcoal. In the heat the reactions are 2SO 3 + S=3SO 2 and 2SO 3 + C = CO 2 + 2SO 2 respectively, and either can be (and is) executed practically in castiron vessels. The presence of carbonic acid in the gas produced by the charcoal process does not interfere with the preparation of sulphites.

The soda salt Na 2 S 2 O 3 + 5H 2 O, known commercially as hyposulphite of soda, is used industrially for chiefly two purposes, namely, (1) as a solvent for chloride of silver in photography (se Photography), —AgCl + Na 2 S 2 O 3 =NaCl + AgNaS 2 O 3 ,—and (2) as an “antichlor” in paper-making, to destroy the remnants of chlorine in bleached paper pulp. To understand its action we need only know that chlorine and water in such cases act like oxygen,— Cl 2 + H 2 O = 2HCl + O; every 4 × 0 thus produced converts one S 2 O 2 of Na 2 OS. 2 O 2 into 2SO 3 of sulphuric acid. For the preparation of this salt a great many methods have been invented. The simplest to explain is the treatment of a solution of normal sulphite of sodium with sulphur,—SO 3 Na. 2 + S = S 2 O 3 Na 2 . Instead of adding free sulphur, Liebig prepares a solution of polysulphide of sodium (by dissolving sulphur in caustic-soda ley) and adds it to the sulphite. The surplus sulphur combines with the sulphite; besides, the polysulphide contains thiosulphate from the first. Another method is to pass sulphurous acid through a solution of sulphide of sodium. Here, by first intention, if we may say so, sulphite of sodium and H 2 S are produced; but the H 2 S and the excess of SO 2 give water and sulphur, and two-thirds of this sulphur unite with the sulphite first formed into thiosulphate. The crude sulphide of calcium, which is produced so largely in the Le Blanc process (see Sodium, supra, p. 243), when exposed to the air gets oxidized, with formation of calcium thiosulphate, which can be extracted by means of water and converted into sodium salt by double decomposition with carbonate or sulphate of soda. Pure thiosulphate of soda forms large transparent monoclinic prisms, which lose no water on exposure to ordinary air in the cold. At about 48° C. they fuse into a liquid, which may remain liquid on cooling, but solidifies suddenly when a fragment of the solid salt is dropped in. 100 parts of water dissolve at 16° 25° 35° 45° C.

65 75 89 109 parts of the salt (Mulder).

The solution is not subject to oxidation in the air.

The anhydride SO 3 is used largely in...