ON THE MANUFACTURE OF PRUSSIATE OF POTASH. 173 
being in that space of time almost wholly dissolved from 
the action of the fused potash and prussiate at the high heat 
required. A shell of the dimensions before described, 
weighing over two thousand pounds, wears away in from 
eight to ten weeks, so that when removed, the iron remain- 
ing will weigh frequently less than two hundred pounds. 
In 1845 there were from twenty to twenty-five such fur- 
naces in operation in the United States, which consumed at 
the rate of three to four thousand tons of animal material, and 
at least 700,000 lbs. of potashes annually, in the manufac- 
ture of prussiate, but the demand for the article having 
diminished, the manufacture is on a considerably reduced 
scale at present. 
The cakes, after cooling, are broken into fragments, 
thrown by portions into a kettle of water set over a furnace 
and heated nearly to boiling, and diligently stirred with a 
long iron chisel to facilitate the solution and prevent the 
adhering of the cakes to the bottom of the kettle, which 
might cause its fracture. Enough cake is thrown in to 
bring the solution to the proper strength, (thirty to thirty- 
two degrees Baume.) The black liquid thus formed, 
consists of potash, prussiate, soda, ammonia, and lime. 
It is strained, while hot, through canvass bags, which 
separate the insoluble impurities into iron kettles set in the 
ground, where it is allowed to stand several days. The 
bags and " black dirt" contained in them which consists 
chiefly of animal charcoal, are subsequently washed to re- 
move the prussiate liquor absorbed by them, and the wash 
liquor used instead of water, for the solution of fresh cake. 
On the cooling of the filtered liquor, the prussiate of potash 
gradually forms on the bottom and sides of the kettles in 
small yellow crystals. After standing a sufficient time, the 
mother liquor is drawn off the crystals, the crude prussiate 
drained and " refined/' by dissolving in hot water, strain- 
ing and crystallizing, until sufficiently pure, which usually 
requires two re-crystallizations. 
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