PREPARATION OP IRON. 305 
and all round the grating a new enclosure of bricks above 
the lower ones. The height of two bricks gives a pro- 
per elevation; it is sufficient that they should be a little higher 
than the vessel for redaction. A rectangular furnace is thus 
constructed twenty -two inches long by fifteen broad. The iron 
pipe traverses the furnace lengthwise ; it rests upon a sup- 
port of bricks upon the grating two inches high. The ad- 
vantage of this support is the prevention of the lower part 
of the pipe becoming more heated than the rest. The fur- 
nace is filled with charcoal so as to cover the pipe, and a 
limited escape is permitted to the ashes, so as not to allow 
the combustion to become too intense. By means of this 
arrangement the heat is never elevated sufficiently to con- 
glomerate the reduced iron. If the temperature is not suffi- 
ciently great, it is perceived by the gas escaping from the 
extremity of the apparatus in as great abundance as it is 
formed. It is necessary then to give a little more activity 
to the fire by increasing the draught. 
The oxide which we employ is the safran of Mars, of 
onr Pharmacopoeias. I should say however that I have 
operated with the oxide of iron, which is produced by cal- 
cining the oxalate. If this were not more costly, this oxide 
would merit the preference, for it contains less oxygen than 
the previousone,and, moreover, possesses less tenuity. It fur- 
nishes the most beautiful preparation. 
It is necessary to remind those who wish to reduce iron 
by hydrogen, that it is necessary to wait before heating, 
until the apparatus has been deprived of air by the first 
current of gas, and that when the operation has terminated 
(which is perceived by no more water escaping) it is neces- 
sary to withdraw the fire and continue to pass the hydro- 
gen, until the apparatus becomes cold. It is very conveni- 
ent to adapt to the apparatus two copper stop cocks, one at 
each end. The current of hydrogen can then be arrested 
without waiting until the pipe becomes cool, as the cocks 
can be closed. When cool, the iron is withdrawn and sub- 
jected to slight porphorizution. — Journ. de Pharm. 
