ON CYANOGEN AND ITS COMPOUNDS. 
233 
also a greater or less proportion of unreduced alkali, and 
deposit them beyond the sphere of action. The combina- 
tion of the nitrogen is effected most rapidly and completely 
when the gas is forced through a long column of alkalized 
charcoal, at a high degree of heat, and under a certain pres- 
sure, and when it experiences obstacles and considerable 
friction in penetrating through the pores of the charcoal and 
interstices between the pieces ; all these conditions are com- 
bined in the most effective manner in the apparatus hereaf- 
ter described. 
After having considered these general questions, it remains 
to determine the most advantageous mode of constructing 
and working the apparatus. The points most worthy of 
attention are the following : — 1st, heating the mixture of 
charcoal and alkali to the highest possible degree and in the 
most uniform manner, and taking the proper precautions 
to recover the vapours of potassium, sodium, and other alka- 
line and saline combinations that may be carried off with 
the waste gases; 2d, to force through the pores and inter- 
stices of the alkalized charcoal a steady current of air or ni- 
trogen gas ; 3d, to protect the mass of cyanized carbon from 
all contact with oxygen during the whole period of heating 
and cooling ; 4th, a continuous operation, which is generally 
so advantageous in manufacturing processes, becomes here 
a necessity, or at least a most important consideration ; be- 
cause, setting aside the waste of fuel, labour and time, the 
dilatations and contractions caused by interruptions of the 
work, occasion a speedy destruction of the apparatus-, on 
this account a perfect steadiness of firing and uninterrupted 
operations are peculiarly desirable. 
The apparatus for carrying out these requisites may be 
varied in dimensions and form, and may be modified to suit 
different carbonaceous matters; but without confining the 
invention to the arrangements of parts herein set forth, two 
applications are described. The first and simplest form con- 
sists of one retort, which is of fire-clay or other suitable ma- 
vol. xi. — NO. III. 21 
