SULPHUR. 



445 



quenee of the cold produced by the evaporation of 

 the portion that flies off, the residue remains liquid. 

 It causes a feeling of intense cold when dropped on 

 the hand. 



Sulphuric acid is obtained by burning a mixture 

 of about seven parts sulphur, and one part nitre, in 

 large chambers, lined with lead. By this combus- 

 tion, sulphurous acid and deutoxide of nitrogen are 

 formed. The deutoxide absorbs oxygen from the 

 atmosphere, and is converted into nitrous acid. 

 Both the acids are absorbed by water. The 

 nitrous acid gives out part of its oxygen to the sul- 

 phurous acid, and converts it into sulphuric acid ; 

 and being reduced to the state of deutoxide, again 

 flies off, unites to oxygen, is converted to nitrous 

 acid, and absorbed by the water. This process 

 goes on till the whole of the sulphurous acid is 

 converted into sulphuric acid. The water, thus 

 acidulated, is evaporated in leaden vessels to a cer- 

 tain point. The evaporation is then continued in 

 glass retorts, till the acid acquires the requisite 

 degree of strength. The ordinary form of a sul- 

 phuric acid lead chamber is the parallelepiped, and 

 its dimensions about seventy feet long, ten or twelve 

 high, and sixteen wide. At the middle height of 

 one end, a small oven is built up, with a cast-iron 

 sole, having a large lead pipe, ten or tw"elve inches 

 in diameter, proceeding from its arched top into 

 the end of the lead chamber. On the sole the sul- 

 phur is burned ; the combustion being aided, when 

 necessary, by heat applied from a little furnace be- 

 low it. Above the flaming sulphur, a cast-iron 

 basin is supported in an iron frame, into which the 

 nitre, equal to one tenth of the sulphur, is put, 

 with a little sulphuric acid. The combustion of 

 the sulphur -is regulated by a sliding door on the 

 oven. In the roof of the remote end of the large 

 chamber, a small orifice is left for the escape of the 

 atmospheric nitrogen, and other incondensable gases. 

 This apparatus is used for the continuous process ; 

 but there is another, or that of the intermitting 

 combustion, which is worthy of notice. Large flat 

 trays, containing the sulphur and nitre, are intro- 

 duced into the interior of the chamber, or into the 

 oven, and fire is applied to the materials. When 

 the sulnhur is burned, and the chamber s filled with 

 sulphurous and nitrous acids, the steam of water is 

 thrown in, in determinate quantity, by a small pipe 

 at the side. This causes a tumultuous motion 

 among the gases and the atmospheric oxygen, which 

 favours the mutual reaction. As the steam con- 

 denses, the sulphuric acid falls with it. After some 

 time, the chamber is aired by opening valves of 

 communication with the external atmosphere. The 

 operation is then commenced anew. Sulphuric acid 

 was formerly obtained by distillation from sulphate 

 of iron ; sixty-four pounds are yielded by six Lun- 

 dred pounds of the sulphate of iron. The following 

 are the properties of pure sulphuric acid. It is col- 

 ourless, has somewhat of an oily or glutinous con- 

 sistency, and hence the ancient name of oil of vitriol. 

 It speedily chars animal and vegetable substances, 

 when .placed in contact with them. It converts 

 vegetable blues to red, and is possessed of an ex- 

 ceedingly acid taste. Acid of the specific gravity 

 1-85, boils at the temperature of 620. The boil- 

 ing point diminishes with the strength. Acid of 

 the specific gravity 1 -78, boils at 435, and acid of 

 the specific gravity 1-G5, at 350. The quantity 

 of water present in one hundred parts of concen- 

 trated and pure sulphuric acid is very nearly 18-46. 

 It consists of three proportionals of oxygen, one of 



sulphur, and one of water ; and by weight, therefore, 

 of 3-0 oxygen 4- 20 sulphur 4. 1-25 water, which 

 equals 6- 125, which represents the combining weight 

 of the concentrated sulphuric acid ; while 34-2 = 

 5, which is the equivalent of the dry acid. Sul- 

 phuric acid strongly attracts water, which it takes 

 from the atmosphere very rapidly, and in larger 

 quantities if suffered to remain in an open vessel 

 imbibing one third of its weight in twenty-four 

 hours, and more than six times its weight in a year. 

 If four parts by weight be mixed with one of water 

 at 50, they produce an instantaneous heat of 300; 

 and four parts raise one of ice to 212. On the 

 contrary, four parts of ice mixed with one of acid, 

 sink the thermometer to 4 below 0. It requires 

 a great degree of cold to freeze it; and, if diluted 

 with half a part or more of water, unless the dilu- 

 tion be carried very far, it becomes more and more 

 difficult to congeal ; yet, at the specific gravity 

 1 -78, it may be frozen by surrounding it with melt- 

 ing ice. Its congelation forms regular prismatic 

 crystals, with six sides. All the simple combusti- 

 bles decompose sulphuric acid with the assistance 

 of heat. At about 400, sulphur converts sulphuric 

 acid into sulphurous acid. Several metals at an 

 elevated temperature decompose this acid, with 

 evolution of sulphurous acid gas, oxidizement of 

 the metal, and combination of the oxide with the 

 undecomposed portion of the acid. Sulphuric acid 

 is of very extensive use in chemistry, as well as in 

 metallurgy, bleaching, and some of the processes 

 for dyeing. In medicine, it is given as a tonic and 

 stimulant, and is sometimes used externally as a 

 caustic. The combinations of this acid with the 

 various bases are called sulphates, and constitute a 

 very important class of salts : for an account of 

 which, see their respective bases. Subsulphurous 

 acid. It has been found, that sulphurous acid has 

 the property of dissolving iron, without the evolu- 

 tion of any gas. The acid gives out half its oxygen 

 to the iron, and converts it into the protoxide of 

 iron, which combines with the acid in question, and 

 which consists of half the oxygen found in sulphur- 

 ous acid. When the salt is decomposed, the sub- 

 sulphurous acid is resolved into sulphurous acid and 

 sulphur. It seems incapable of existing except in 

 combination with a base. When insulated, half 

 the sulphur separates, and sulphurous acid remains. 

 The hyposulphurous acid also seems incapable of 

 existing except in combination with a base. When 

 sulphuric acid in a slight excess is poured into a di- 

 lute solution of hyposulphite of strontites, the whole 

 strontites is thrown down, and the filtered liquid 

 consists chiefly of a solution of hyposulphurous acid 

 in water. This liquid is transparent and colourless, 

 is destitute of smell, and has an acid, astringent, 

 and very bitter taste. On standing a few hours, it 

 undergoes spontaneous decomposition, the liquid 

 becomes milky, sulphur is deposited, and sulphurous 



acid remains in solution Hjiposulphuric acid. By 



causing a current of the sulphurous acid gas to pass 

 through black oxide of manganese, suspended in 

 water, a neutral salt is formed, which, when dis- 

 solved, consists of a mixture of neutral sulphate and 

 hyposulphate of manganese. By pouring into this 

 solution barytes water, the whole of the sulphate 

 of manganese is thrown down, while the hyposul- 

 phate is converted into hyposulphate of barytes, 

 which remains in solution. A current of carbonic 

 acid throws down any excess of barytes that may 

 have been added ; and then, by evaporating the 

 liquid, the hyposulphate of barytes is obtained in 



