POTASSIUM AND SODIUM. 
281 
ammonia; cyanide of the metallicbase is thus produced, and 
this product is constantly augmented in quantity (the current 
of ammonia being continued) until great part of the alkali, 
or other compound of its base, has become converted into 
cyanide. When an alkaline carbonate is used, powdered 
charcoal to the amount of more than 30 per cent, of its weight 
may be added, without destroying the fluidity of the mix- 
ture if the temperature is raised to a full red. When the 
potash or soda is in a caustic state, a larger proportion of 
charcoal may be added; or, what is more advantageous, the 
mixture will remain fluid, although the heat he raised not 
so high. Whether the ammonia gas is passed through the 
mixture of carbon and fused alkali, or other compound of its 
metallic base (which is preferred), or over its surface, it is 
better to have more than one vessel charged with the heated 
materials, and so connected together by pipes, that the nitro- 
gen of the ammonia, which escapes the chemical reaction 
in the first vessel, shall not pass through the whole series 
without combining. The apparatus thus acts on the prin % 
ciple of a series of Woolfe's bottles, and according to this 
invention all the vessels are made red-hot, except the last, 
jnto which water, or some liquid convenient for arresting 
the vapours of alkaline metal, is put; or otherwise the va- 
pours might be lost. The first product, as in the common 
process for making prussiate, is a cyanide, of the alkaline 
metal present, which may be dissolved out from the mass, 
technically called " metal," by boiling the latter in alcohol, 
of about 0-896 specific gravity, from which, filtered hot, it 
spontaneously separates, in great part, on cooling. To ob- 
tain the ferrocyanide, the metal is to be treated in the usual 
way, namely, its soluble parts dissolved in water, then 
treated with iron, the solution evaporated, and when suffi- 
ciently concentrated and clear, set aside to crystallise ; and 
the rough product is afterwards purified by recrystallisation 
The patentee states, that he does not claim the invention 
of any process for dissolving out or obtaining either cyanide 
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