180 ON THE MANUFACTURE OF PRUSSIATE OF POTASH. 
nace, or flue, heated to whiteness, which surrounds the 
cyhnder. 
The mixture of charcoal and potash is exposed during 
about ten hours, to the current of strongly heated gases, 
which penetrate the mass in all directions. The apparatus 
works continuously, the cylinder being fed from the top, 
in proportion to the quantity removed by an extractor at 
the bottom, which allows a determined proportion to escape 
regularly. 
The cyanized charcoal after cooling in a cast iron re- 
ceiver, into which it passes from the fire brick cylinder, falls 
into a reservoir containing water and native carbonate of 
iron. The liquors are evaporated and the prussiate crys- 
talized in the usual manner. 
The proportion of cyanide obtained by this process, from 
a certain quantity of potash, is greater with the nitrogen of 
the air, than with animal material according to the old 
method. , . 
Soda acts in a similar way with potassa, but requires a 
still higher temperature. 
Coke produces less cyanide than wood charcoal. The 
presence of the vapour of water, even in small quantity, 
diminishes the product of cyanide, or at least decomposes 
it as it is formed, giving ammonia. 
Finally, pure nitrogen produces the cyanides more readily 
than when mixed with carbonic acid or oxide. 
M. Pelouze observes that the consumption of animal 
material in France, in the fabrication of prussiate of potash, 
amounts to 3,000,000 kilogrs., (about 3,000 tons^ annually, 
and remarks as one of the incidental advantages of the 
new method, that its adoption would save for agricultural 
uses this large quantity of animal matter. 
