Sulphuric Acid.—One of the most important chemical agents required in the arts and manufactures, is used very extensively for making soda-ash for bleaching linen, woollens, etc., straw, etc.,[181] manure making, and for a variety of chemical productions; also for refining metals.[182]
Soda-ash (alkali) is obtained from common salt by means of concentrated sulphuric acid. It is used instead of barilla for soap-making, as a substitute for pot and pearl ashes in glass-making; for cleaning and bleaching; and, in the form of carbonate, for medicinal and domestic purposes. In the year 1862 the enormous quantity of from 100,000 to 120,000 tons of the former, and from 25,000 to 30,000 tons of the latter, was made in Great Britain alone.[183] That quantity is now vastly increased.[184]
Manures.—A great consumption of sulphuric acid has of late years taken place for agricultural purposes,[185] viz., in the preparation of superphosphate of lime, the most active manure for turnips, grass, and cereals.
Oïdium.—Within the last few years it has been discovered that the use of flowers of sulphur, containing traces of sulphuric and sulphurous acid, and of carburetted hydrogen, is a protection against the vine disease—oïdium. Although no reliable information exists as to the exact quantity used for this purpose, yet it is known to be very considerable.
Flowers of sulphur have recently been strongly recommended as a remedy for the potato disease.[186]
Such are a few of the principal objects to which sulphur is devoted, and for which it is needed; thereby proving most conclusively that THE CONSUMPTION IS ONLY LIMITED BY THE SUPPLY.
Sulphur is found in Corfu, the neighbourhood of Rome, Transylvania, Spain, the clear or borax lake in California, the slopes of the Popocatepetl, in the province of Puebla, Mexico; in Montana, North America, and in the Andaman and the Japanese islands. Supply from these sources is practically impossible, and the whole supply of sulphur to Europe and America is derived from the Sicilian sulphur-deposits, the imports of which into this country arose from 16,686 tons in 1842 to 58,204 tons in 1859,[187] and over 75,000 tons in 1862;[188] and in France, from 6668 tons in 1820 to 33,361 tons in 1855.
Sulphur is found either (a) in a pure native state, (b) as gas, or (c) in mechanical admixtures with clays or other earths. The method of extraction of sulphur when mechanically combined with foreign substances is thus described in Richardson and Watts’ “Chemical Technology,” vol. i., part iii, p. 314:
“It has already been noticed that the deposits of sulphur are always associated with various mineral or earthy matters, and three processes are followed to separate the principal part of these impurities, which generally amount to more than one-half of the entire weight of the deposit.
“When the deposit is rich in sulphur it is melted in a cast-iron pot, heated by an open fire. The melted mass is stirred with an iron rake to facilitate the separation of the earthy matters, which are allowed to fall to the bottom. The liquid sulphur is then removed by a ladle, thrown into an iron vessel, and allowed to solidify. The temperature ought to vary between 250° and 300° Fahr., and never reach 480°, at which point the sulphur would take fire. The residue which remains, and contains more or less sulphur, is removed, and may be treated by either of the following plans: