No. 11. 



Manufacture of Sulphuric Acid. 



331 



must still claim your attention to a few more 

 of its most important and immediate results. 

 I have already told you, that in the manu- 

 facture of soda from culinary salt, it is first 

 converted into sulphate of soda. In this 

 first part of the process, the action of sul- 

 phuric acid produces primary muriatic acid 

 to the extent of one and a half the amount 

 of the sulphuric acid employed. At first 

 the profit upon the soda was so great that 

 no one took the trouble to collect the muri- 

 atic acid; indeed it had no commercial value. 

 A profitable application of it was, however, 

 soon discovered : it is a compound of chlo- 

 rine, and this substance may be obtained 

 from it purer than from any other source. 

 The bleaching power of chlorine has long 

 been known; but it was only employed upon 

 a large scale after it was obtained from resi- 

 duary muriatic acid, and it was found that 

 in combination with lime it could be trans- 

 ported to distances without inconvenience. 

 Thenceforth it was used for bleaching cot- 

 ton; and, but for this new bleaching process, 

 it would scarcely have been possible for the 

 cotton manufacture of Great Britain to have 

 attained its present enormous extent — it 

 could not have competed in price with 

 France and Germany. In the old process 

 for bleaching, every piece must be exposed 

 to the air and light during several weeks in 

 the summer, and kept continually moist by 

 manual labour. For this purpose, meadow 

 land, suitably situated, was essential. But 

 a single establishment near Glasgow, bleach- 

 es 1,400 pieces of cotton daily, throughout 

 the year. What an enormous capital would 

 be required to purchase land for this pur- 

 pose ! How greatly would it increase the 

 cost of bleaching to pay interest upon this 

 capital, or to hire so much land in England ! 

 This expense would scarcely have been felt 

 in Germany. Beside the diminished ex- 

 pense, the cotton stufl% bleached with chlo- 

 rine suffer less in the hands of skilful work- 

 men than those bleached in the sun ; and 

 already the peasantry in some parts of Ger- 

 many have adopted it, and find it advantage- 

 ous. 



Another use to which cheap muriatic acid 

 is applied, is the manufacture of glue from 

 bones. Bone contains from 30 to 36 per 

 cent, of earthy matter — chiefly phosphate 

 of lime, and the remainder is gelatine. 

 When bones are digested in muriatic acid, 

 they become transparent and flexible }ike 

 leather, the earthy matter is dissolved, and 

 after the acid is all carefully washed away, 

 pieces of glue of the same shape as the 

 bones remain, which are soluble in hut water 

 and adapted to all the purposes of ordinary 

 glue, without further preparation. 



Another important application of sulphu- 

 ric acid may be adduced, namely, to the re- 

 fining of silver and the separation of gold, 

 which is always present in some proportion 

 in native silver. Silver, as it is usually ob- 

 tained from mines in Europe, contains, in 

 16 ounces, 6 to 8 ounces of copper. When 

 used by the silversmith, or in coining, 16 

 ounces must contain in Germany 13 ounces 

 of silver, in England about 14-|. But this 

 alloy is always made artificially, by mixing 

 pure silver with the due proportion of the 

 copper; and for this purpose the silver must 

 be obtained pure by the refiner. This he 

 formerly effected by amalgamation, or by 

 roasting it with lead ; and the cost of this 

 process was about £2 for every hundred 

 weight of silver. In the silver so prepared, 



about 72V0" t° SoW^h P^'"^ of gold remained. 

 To effect the separation of this by nitric hy- 

 drochloric acid was more expensive than the 

 value of the gold; it was therefore left in 

 utensils, or circulated in coin, valueless. The 

 copper, too, of the native silver was of no 

 use whatever. But the y oW P^'"'^ ^^ S"^*^* 

 being about one and one-half per cent, of the 

 value of the silver, now covers the cost of 

 refining, and affords an adequate profit to 

 the refiner; so that he efl^ects the separation 

 of the copper, and returns to his employer 

 the whole amount of the pure silver, as well 

 as the copper, without demanding any pay- 

 ment: he is amply remtinerated by that mi- 

 nute portion of gold. The new process of 

 refining is a most beautiful chemical opera- 

 tion. The granulated metal is boiled in con- 

 centrated sulphuric acid, which dissolves 

 both the silver and the copper, leaving the 

 gold nearly pure, in the form of a black 

 powder. The solution is then placed in a 

 leaden vessel containing metallic copper; 

 this is gradually dissolved, and the silver 

 precipitated in a pure metallic state. The 

 sulphate of copper is also a valuable product, 

 being employed in the manufacture of green 

 and blue pigments. 



Other immediate results of the economical 

 production of sulphuric acid, are the general 

 employment of phosphorus matches, and of 

 stearine candles — that beautiful substitute 

 for tallow and wax. Twenty-five years ago, 

 the present prices and extensive applications 

 of sulphuric and raariatic acids, of soda, 

 phosphorus, &c., would have been consi- 

 dered utterly impossible. Who is able to 

 foresee what new and unthought-of chemical 

 productions, ministering to the service and 

 comforts of mankind, the next twenty-five 

 years may produce 1 



After these remarks you will perceive 

 that it is no exaggeration to say, \ve may 



