OTHER PROPOSED 3firriions os Paonuonorr.—The first attempt to make sulphuric acid from a mixture of sulphurous acid and oxygen by condensation in platinum was made by Phillips. According to his plan sulphurous acid from the combustion of sulphur is mixed with an excess of atmospheric air and forced through a red-hot tube of cast iron packed with platinum, sponge, or other material by means of a blast of hot air. The gaseous sulphuric acid produced is carried with the oxygen and excess of air into the bottom of an upright leaden cylinder filled with flints, whilst water flows down the cylinder and keeps the flints constantly wet. As the gases ascend the. sulphuric acid contained in them condenses and flows away from the bottom of the cylinder with the water produced, while the freed gases escape into the air.
Platinum has been found so expensive as to be partially or wholly abandoned. Piria has adopted pumice impregnated with a solution of platinum, and made red hot so that a film of platinum is formed all over it.
Schneider and Laming have patented an apparatus in which pumice causes the formation of the acid. The pumice is packed in a series of upright tubes heated to about 300° (572° F.), in which the gases circulate.
Schmersohl and Bouk pass sulphurous acid, air, and steam through horizontal stoneware or cast-iron pipes filled with asbestos, pumice, or other porous bodies, and strongly heated.
Petrie employs an upright cylinder of stoneware or enamelled cast iron heated to 300° and filled with flints constantly moistened from above.
Besides these, multifarious plans have been devised for extracting the sulphuric acid from natural sulphates, such as gypsum, but no one has been found to possess such qualities as to present any likelihood that the current system of oxidizing sulphur will be displaced. Hargreaves' method for making sulphate of soda from salt, however, will in all likelihood supplant the use of sulphuric acid in this enormous branch of chemical industry.
USES.—The uses of sulphuric acid are more varied and numerous than those of auy other chemical product.
This acid is required in the formation of sulphates, such as those of ammonium, aluminium, copper, iron, magnesium (Epsom salts), mercury (for corrosive sublimate and calomel making), potassium, sodium (Glauber's salt), and indirectly in the production of alum. It is used in the
manufacture of nearly all other acids of importance, as bored°, citric, fluoric, hydrochloric, nitric, phosphoric, steario, sulphurous, and tartaric acids. It is used in cleaning metals ; in the manu facture of tin-plate ; in exciting electric currents for various purposes, and for the evolution of hydrogen gas. It is further used in the ether, of ozokerite, of blacking, and of a variety of other substances of minor importance. Also in the separation of pure hydro-carbons from tars; in the purification of oils; and it is largely consumed in the removal of fats from cotton and woollen goods. Other applications of this acid are in the elimination of sugar from starch, and the precipitation of lime from molasses ; in dissolving indigo ; in giving a dark colour to wood ; and in the preparation of aniline and madder dyes. Bleaching and dyeing consume large quan tities of sulphuric acid. In the preparation of collodion, gun-cotton, uitro-benzol, nitro-glycerine, picric acid, &o., &c., 'it is also largely used. Enormous quantities are annually required for the manufacture of mineral waters, and still more for the conversion of mineral phosphates into super phosphates. It is also valuahle in the preparation of other fertilizers, such as blood-manures and sewage, by fixing the ammonia and arresting fermentation ; in the removal of bad smells from casks, &a, by destroying fungoid growths ; it thus acts the part of a deodorizer. But the moat important of all its uses is for the conversion of common salt into sulphate of soda, in the manu facture of alkali. In the laboratory it forms one of the most useful reagents in the hands of the analytical chemist; moreover its great hygroscopic powers make it invaluable as a desiccating agent. The uses of this acid are indeed so numerous that it would be difficult to prescribe limits to its application.