TECHNICAL CHEMISTRY. 



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manufacture by Berthollet's application of chlorine to the 

 bleaching of cotton goods sulphuric acid being needed 

 for the formation of this element ; and from that time up 

 to the present the demand for sulphuric acid has gradually 

 increased, until it appears now to be almost unlimited. 

 According to the valuable statistics of Mr. Mactear, the cost 

 of manufacture in the year 1798 was 321. per ton, and the 

 selling price from 50/. to 60Z. 



The next improvement consisted in making the operation 

 continuous. For this purpose a brick furnace was attached 





FIG. 4. 



sometimes to one, and sometimes to two chambers, as shown 

 in Fig. 4. In this the mixture of sulphur and nitre was 

 burnt, the gases first passing into one, and afterwards 

 being allowed to pass into the other chamber. One hundred 

 parts by weight of sulphur was thus made to yield 200 

 parts by weight of sulphuric acid, and to need fifteen per 

 cent, of nitre. According to theory, 100 parts of sulphur 

 can yield 306 parts of pure sulphuric acid, and it is now 

 found possible to obtain by careful working no less than 

 300 parts of acid, whilst only four parts of nitre are 

 needed. From this you will see how accurately it is now 

 possible to carry on the process. About the year 1814 jets 

 of steam were thrown into the chamber instead of water 

 being placed on the floor, and from that time forward 

 the system of manufacture has undergone no essential 



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