ON THE MANUFACTURE OF PRUSSIATE OF POTASH. 171 
ing a reverberatory furnace of similar construction in other 
respects. 
Pine wood or rosin is the fuel usually employed, coal 
has been tried, but we believe unsuccessfully. A chimney 
having a good draught is required, and much of the success 
of the manufacture depends upon the proper construction 
of the furnace, and disposition of the flues, so as to maintain 
a steady and sufficient heat, as under a full red, prussiate is 
not formed ; and, on the other hand, not to have the heat 
and draught too great, which would cause waste by subli- 
mation of potash and too rapid combustion of animal mate- 
rial. • 
The furnace having been heated to full redness, the charge 
of potash is thrown into the shell, and when it is perfectly 
fused, four or five lbs. of iron filings are added and stirred 
in, the fuel in the fire hole removed or allowed to burn out, 
and through the working door, the animal material is in- 
troduced, a shovel full at a time, each portion being mixed 
well into the potash with a long iron poker, until the mass 
becomes homogeneous, and the flame nearly ceases. When 
the full charge of material has been mixed in, the working 
door is closed, and a few billets thrown into the fire-hole, 
the flame from which is sufl"ered to play over the mixture 
until it is tfioroughly fused. The red hot pasty mass is 
then briskly stirred with the poker for a few minutes, and 
finally ladled out with a long-handled iron ladle, into a pan 
or an old shell, where it concretes on cooling into a solid 
mass of a green colour externally , darker within, and having 
a somewhat crystalline fracture, which is technically called 
the '* cake." It usually requires about half an hour to melt 
the potash, one and a half or two hours to mix in the ani- 
mal material, and fifteen minutes to cook the cake." 
From sixty to eighty lbs. of good commercial potash are 
employed for a charge, and about twice its weight of ani- 
mal material, consisting of horns, hoofs, dried blood, greaves 
from the tallow chandlers, woollen rags or leather, 
