SULPHUR 



795 



usefully employed for the extinguishing of fire 

 as, for example, in chimneys. 



Snlphnr occurs very widely distributed in the 

 mineral kingdom, partly free and partly combined 

 with other elements. The free sulphur is either 

 found pure in regularly formed crystals, or inti- 

 mately mixed with earthy matters. Sulphur is 

 usually plentiful in volcanic districts; most of 

 what is used in Europe has been obtained from 

 Sicily (which in 1880-90 exported from 213,000 to 

 350,000 tons yearly), but of late large quantities 

 are recovered from the waste of soda manufacture, 

 and sulphur has been actually exported from New- 

 castle to Italy (see SODA, p. 553). Sulphur is found 

 in many parts of the United States, and some 

 Californian deposits have been utilised to a small 

 extent, but have teen unable to compete with 

 Sicilian sulphur. In the form of sulphide, sulphur 

 occurs abundantly in combination with iron, 

 copper (iron and copper pyrites), lead (galena), 

 zinc (blende), &c., the bisulphide of iron (or 

 iron pyrites) furnishing most of the sulphur 

 that is employed in the manufacture of sul- 

 phuric acid. Many of the metallic sulphides 

 (formerly known as Sulphurets) occur native, and 

 form highly valuable ores. They are all solid at 

 ordinary temperatures, and, with the exception of 

 those of potassium, sodium, calcium, strontium, 

 barium, and magnesium, are insoluble in water ; 

 they are, moreover, conductors of electricity. 

 Many of them, especially of those that occur native, 

 exhibit very brilliant and characteristic colours. 

 The same metal may have several sulphides, and 

 in general there is a sulphide for each oxide. The 

 sulphides are, however, sometimes the more numer- 

 ous. Sulphur is still more extensively distributed 

 in the form of sulphates, as in the sulphates of 

 lime, magnesia, baryta, &c. In the vegetable 

 kingdom sulphur is a constituent of Albumen 

 (q.v.), and of the volatile irritant oils of mustard, 

 garlic, asafoetida, &c. ; moreover vegetable juices 

 contain it in the form of certain sulphates. In 

 the animal kingdom it is not only a constituent 

 of the albuminous, fibrinous, and gelatinous tissues, 

 but of the hair, saliva, bile, urine, &c. 



The grosser impurities of sulphur are removed by 

 crude processes of fusion and distillation at or 

 near the place from whence it is obtained. What is 

 called refined sulphur is purified by distillation in a 

 large cast-iron still, and condensed in a receiver 

 kept cool. When the vaporised sulphur is con- 

 densed in a large chamber it is obtained in the 

 form of sublimed sulphur, or flowers of sulphur ; 

 but as the walls get hot it melts and collects on 

 the floor, and is run into cylindrical wooden 

 moulds, from which, when cool, it is taken out as 

 roll or stick sulphur. The residue left in the 

 retort is a mixture of sulphur with various im- 

 purities. Under the name of black sulphur, or 

 Sulphur viritm, it is used in veterinary medicine, 

 ana for the purpose of dressing mouldy hops. 

 Sulphur is thrown down from certain of its com- 

 pounds (as from a strong solution of a polysulphide 

 of calcium, sodium, or potassium) by dilute hydro- 

 chloric acid ; it falls as a grayish-white, very fine, 

 light powder, known in the Materia Medica as 

 milk of sulphur, or precipitated sulphur. The 

 most common impurities met with in ordinary 

 commercial sulphur are selenium and realgar ( bisul- 

 phide of arsenic). Flowers of sulphur frequently 

 exhibit a slight acid reaction, in consequence of a 

 little sulphurous acid clinging to them. By rinsing 

 them with water this impurity is at once removed. 

 Sulphur is extensively employed in the arts and 

 manufactures, as in the manufacture of some 

 matches, gunpowder, &c. When converted into 

 sulphurous acid it is employed as a powerful 

 bleaching agent, as also for the destruction of 



insects, fungi, &c. ; but its chief consumption is in 

 the manufacture of sulphuric acid. 



The eight compounds of sulphur and oxygen, 

 when combined with water, present the characters 

 of acids. These acids have this composition : 



Hyposulphurous acid H 2 S0 2 



Sulphurous HoSOs 



Sulphuric H,SO 4 



Thiosulphuric H 2 "S.,O 3 



Dithionic 

 Trithionic 

 Tetrathionic 

 Peutathionie 



We shall here notice the most important members 

 of this group the second, third, and fourth; the 

 third, Sulphuric Acid, is discussed in a special 

 article. (The last four derive the essential part 

 of their name from the Greek theion, 'sulphur. ) 



Sulphurous Anhydride (often called Sulphurous 

 Acid ), SO 2 , occurs under the ordinary relations of 

 temperature and pressure as a colourless gas, possess- 

 ing the suffocating odour of burning sulphur. In 

 its concentrated form it is quite irrespirable, and in 

 a diluted state it excites cough. It not only is 

 incapable of burning, but it rapidly extinguishes 

 the flame of burning bodies. It is very freely 

 soluble in cold water, which at 32 (0 C.) takes up 

 nearly 69 times its volume of the gas, while at 

 75 (24 C.) it only takes up 32 volumes; the 

 solution known as Aqueous Sulphurous Acid 

 having at first the same smell and taste as the 

 gas, but soon absorbing oxygen from the air, and 

 becoming converted into sulphuric acid. By the 

 action of cold sulphurous acid may be condensed to 

 a colourless transparent limpid liquid, which freezes 

 at - 105 ( - 76 C. ), forming a transparent crystal- 

 line solid. The specific gravity of the gas is 2 '247 

 (atmospheric air being the unit), and that of the 

 liquid is 1'49 (water being the unit), the solid 

 being considerably heavier. Although dry sulphur- 

 ous acid gas and dry oxygen when mixed exert no 

 action on one another, there are many conditions 

 under which sulphurous acid rapidly absorbs oxygen, 

 and is converted into sulphuric acid e.g. if the gas 

 be dissolved in water ; a similar action takes place 

 under the influence of hydrated nitric acid, iodic 

 acid, and certain metallic oxides. Hence sulphur- 

 ous acid is a powerful reducing or deoxidising 

 agent. This gas is a common and abundant pro- 

 duct of volcanic action, and is occasionally met 

 with in solution in the springs in volcanic regions. 

 It may be prepared artificially by simply burning 

 sulphur in the air or in oxygen gas, or by heating 

 in a flask 4 parts of flowers of sulphur mixed with 

 5 parts of powdered black manganese, sulphur- 

 ous acid and sulphide of manganese being the pro- 

 ducts, as shown by the equation S, + Mn0 2 = SO a 

 + MnS. In consequence of its solubility in water 

 this gas should be collected over mercury. In 

 addition to the uses of sulphurous acid as a bleach- 

 ing agent, it is valuable both as a disinfectant 

 agent and as a powerful antiseptic, and has been 

 used as an application for lumbago, &c. But by far 

 its most important use is in the manufacture of 

 sulphuric acid. In combination with bases this 

 acid forms the sulphites a class of salts which, 

 excepting the sulphite of soda, are of little import- 

 ance, except for their power when moist of extract- 

 ing oxygen, and thus acting as reducing agents. 

 The salts of the sesquioxide of iron are reduced by 

 them to salts of the protoxide. 



Thiosulphuric Acid, H 2 S 2 O.,, formerly called 

 Hyposulphurous Acid, is, as yet, only known in a 

 state of combination with bases ; for on attempt- 

 ing to separate the acid from the base the former 

 becomes decomposed into sulphur and sulphurous 

 acid. The most important of its salts is the Hypo- 

 sulphite of Soda, Na-S^Oj + 5H 2 O, described in 

 the article SODIUM. This and other soluble hypo- 



