PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 883 



apparatus, as there was no establishment Avest of the Alleghany 

 mountains at that time. It is well known that the salt has to be 

 decomposed by the oil of vitriol, in order to obtain a residuum, 

 which is the base of all the varieties of ash. It required a large 

 amount of acid. For instance, 13,000 pounds of salt required 

 10,000 pounds oil of vitriol to produce 15,000 pounds hydrochlo- 

 ric acid, and the residue is called salt cake or sulphate of soda. 

 The sulphuric acid, as it comes from the chambers, stands at but 

 48° B. It is too weak for practical use, and requires concentra- 

 tion. It is therefore necessary to perform this operation in a pla- 

 tinum vessel, made like a common still or alembic, of forty gal- 

 lons capacity. The oil vitriol at first obtained is concentrated in 

 shallow lead pans; on getting stronger, the acid, while warm, will 

 attack the lead, and recourse must be bad to glass or platinum 

 retorts, which are placed in an iron envelop. The partially con- 

 centrated acid passes through a pipe into a retort, where it boils; 

 then it passes out by a Liebig cooler into a cooling box containing 

 two lead pipes. The weak acid vapors escape through a pipe in 

 the top, and are condensed in another chamber. The acid running 

 out through the last cooling apparatus is 66° B, and out of this 

 still twenty-four carboys per day are obtained. The price of such 

 a still, imported from France, is $15 000 in gold. The uses of 

 oil vitriol are manifold; not only for the conversion of the salt 

 into sulphate, and thereby obtaining hydrochloric acid, but also 

 for the purpose of manufacturing aqua fortis, oi- nitric acid, by the 

 decomposition of nitrate of soda, or potash; if from soda, salt-cake 

 is likewise ol)tained, and if from potash, the sulphate of potash is 

 the result, which is used in the manufacture of potash alum. 



The company has agents in New York, Philadelphia, Boston 

 and elsewhere, to purchase from other chemical works the salt- 

 cake, paying $10 to $12 per ton, and as much more for freight to 

 its place of destination. 



For all these operations the compan}' digs 3,000 bushels of their 

 own coal per day, and produce their concentrated lye, put up in 

 cans, and prepared l\y calcining 100 pounds of salt-cake with 55 

 pounds of charcoal and 120 pounds of chalk. 



The progressive Yankee spirit, always on the alert for improve- 

 ments and inventions, has entered into the minds of our Philadel- 

 phia friends since hearing that, for some years back, soap factories 

 and chemical works in Paris were supplied with a new material 

 for the production of their alkali, and learning it was the mineral 



