CHAMBERS'S INFORMATION FOR THE PEOPLE. 



'be presently noticed, 21,161 hundredweight (valued 

 .at 52,953) were imported into England from India 

 in 1869. Borax is also prepared from a mineral 

 -called hayesine, which is a native calcium borate 

 scattered over dry plains in southern Peru. 



In the volcanic districts of Tuscany, a native 

 boracic, or, as it is sometimes called, boric acid, is 

 obtained from the water of boiling springs which 

 -issue from the ground in the form of jets of steam, 

 called soffioni. From this borax is formed by the 

 addition of sodium carbonate. These are directed 

 into lagoons or artificial basins, which are scattered 

 over a surface of about thirty miles, and are con- 

 stantly giving off clouds of smoke, the district 

 'being subject to constant shocks produced by sub- 

 terranean agencies. These basins are constructed 

 of coarse masonry, each large enough to contain a 

 few soffioni, and six or eight of them are placed 

 at different levels on the hill-side. Into the upper- 

 most basin the hot springs are allowed to flow ; 

 and after remaining twenty-four hours, during 

 which time the water is kept in constant agitation 

 by subterranean vapour, it passes by means of a 

 pipe into the next lower basin. Here it remains 

 another twenty-four hours, and, of course, takes 

 up an additional quantity of boracic acid. In this 

 way, the water passes through each successive 

 foasin, till, in the last, it contains about 0*5 per 

 cent, of boracic acid. This weak solution is then 

 evaporated in long leaden tanks placed low down 

 in the ground, and ingeniously heated with steam 

 produced by subterranean heat. This method 

 was first applied by Count Larderel in 1817, and 

 has had the effect of converting, although slowly, 

 an unprofitable branch of industry into the most 

 important chemical manufacture of Italy. The 

 concentrated solution of boracic acid is finally 

 crystallised in tubs, and then spread out on the 

 floor of a hot chamber to dry. The product thus 

 obtained is the boracic acid of commerce ; but 

 this usually contains only about seventy-five per 

 cent, of the pure acid, the other impurities being 

 chiefly sulphates of ammonia and magnesia. The 

 annual produce of boracic acid in Tuscany was, a 

 few years ago, about two thousand tons, valued at 

 more than ^400,000, and it has been gradually 

 increasing. Borax is most largely consumed in 

 the making of glazes for pottery, but it is also 

 used in the manufacture of some kinds of glass, 

 in dyeing, candle-making, and chemical opera- 

 tions, for soldering, and as a flux in metallurgy. 



Baryta and Strontia. Both of these are 

 alkaline earths. There are two native com- 

 pounds of baryta namely, barytes, heavy-spar, 

 or barium sulphate ; and witherite, or barium 

 carbonate. The sulphate is used as a pigment, 

 sometimes by itself, but more frequently mixed 

 with white-lead. The carbonate is employed to 

 some extent in the manufacture of pottery and 

 glass, and in chemical works. 



SULPHUR AND SULPHUR ORES. 



The well-known elementary substance sulphur, 

 or brimstone, is a yellow, brittle mineral of great 

 commercial value. Native sulphur occurs in all 

 volcanic regions in cavities and fissures of lava. 

 In other places, it is commonly associated with 

 beds of gypsum and rock-salt ; and it is likewise 

 found as a deposit about sulphurous springs, and 

 in situations where there is decomposing iron 



398 



pyrites. Almost the whole of this substance used 

 in England (except what is obtained from pyrites) 

 is brought from Sicily, where the gypsum and 

 sulphur bearing formation covers a large portion 

 of the island. The geological position of these 

 beds is not yet accurately ascertained ; for a long 

 time they were supposed to be secondary rocks, 

 but some recent observers think they rather 

 belong to the Tertiary period. The sulphur is 

 found in gypsum and limestone 'as a uniform 

 or irregular mixture, sometimes concentrated in 

 small parallel seams.' In clay and slate, on the 

 other hand, the sulphur is found 'concentrated 

 in globular masses.' There are some 50 mines 

 in Sicily, employing about 20,000 hands. The 

 annual produce of the island is now nearly 

 200,000 tons ; and of all Italy, about 300,000 tons, 

 representing a money value of .1,200,000. 



Partly owing to the consumpt of sulphur in 

 recent years for the vine disease, but no doubt 

 more largely on account of the ever-increasing 

 demand for it in the manufacture of sulphuric 

 acid the key-stone of our chemical manufactures 

 iron pyrites is now extensively employed as an 

 ore of sulphur. This mineral is a bisulphide of 

 iron, containing, when pure, 53'3 per cent, of 

 sulphur, and 46-6 per cent of iron. Iron pyrites 

 is abundantly diffused. In Cornwall, where much 

 is annually mined, it is called numdic, and occurs 

 in veins ; and in Northumberland and Durham, 

 where the annual yield is also large, it is called 

 brasses, and is either picked or washed out of the 

 coal. It is also extensively mined in Yorkshire, 

 Lancashire and Wales, and a little is found in 

 Wicklow. 



From 30,000 to 70,000 tons of sulphur ores, 

 mainly pyrites, are raised in the United Kingdom. 

 The annual imports, mainly from Spain and 

 Portugal, amount to hundreds of thousands of 

 tons, with a value of more than a million of pounds. 



Native sulphur is employed to make the purer 

 kinds of sulphuric acid. It is also used to bleach 

 wool and silk, as a disinfectant, in the manufac- 

 ture of gunpowder, in medicine, and for many 

 other purposes. Sulphuric acid made from pyrites 

 is never quite free from arsenic. 



GRAPHITE OR PLUMBAGO. 



Closely allied to the diamond, which comes 

 first under our next head, is graphite, plumbago, 

 or black-lead. The finer kinds of this substance 

 consist of nothing but carbon, but more usually 

 it contains some oxide of iron and clay. Perhaps 

 the finest plumbago in the world for pencil-making 

 is that obtained from the celebrated mine at 

 Borrowdale, in Cumberland. The supply is, how- 

 ever, very irregular, as the mineral is found only 

 in detached pieces in nests of trap-rock. Some 

 years ago, a large quantity was got, and stored 

 away by the proprietors, of which small quantities 

 have been sold from time to time. The mine is 

 supposed to be nearly exhausted, and has not 

 been worked for several years. Plumbago of 

 good quality is obtained in several parts of the 

 world. Besides the use of the finer kinds in 

 pencil-making, black-lead is employed in the con- 

 struction of crucibles for metallurgical purposes, 

 for giving a gloss to iron articles, and for lubri- 

 cating machinery. 



