TECHNICAL CHEMISTRY. 



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placed in the iron pan, and on to this is run the quantity 

 of sulphuric acid necessary completely to decompose it. 

 This amounts to 123*5 gallons, or 1800 Ibs. of chamber-acid 

 having a specific gravity of 1'42. Torrents of hydrochloric 

 acid are then given off, the decomposition which takes 

 place being represented by the equation 



H 2 S0 4 + NaCl - HNaS0 4 + HC1. 



This process lasts about] one hour, and the temperature 



of the mass rises to about 120 Fahr. All the hydrochloric 

 acid which is thus evolved passes directly from the pan by 

 means of the flue (e) Fig. 8 into the hydrochloric acid con- 

 densing towers (Fig. 10). These towers are often 50 or 60 

 feet in height, and are usually built of Yorkshire flag 

 clamped together with iron, the joints being rendered gas- 

 tight by a cord of vulcanized rubber. 



