304 
PREPARATION OF IRON. 
without doubt, but of importance, if it be desirable not to 
lose considerable quantities of hydrogen gas. 
We have confined ourselves to the employment as a ves- 
sel of one of the fountain pipes found in commerce. That 
which we employed was 4i inches in diameter, and 22 in 
length. Such a vessel furnished from 9 to 11 oz. of iron 
by the operation. 
To multiply the surfaces and diminish the proportion of 
inactive gas, we placed in the tube small floors (dia- 
phragms) of iron gauze, between which were thin bars, the 
gauze being covered with the oxide ; when all were ar- 
ranged, they presented a solid mass. As the operation pro- 
ceeded, the powder sank down and the passage of the gas 
was free. 
Besides the pipe of reduction, the apparatus is composed 
of a large flask for the production of hydrogen gas, of a wide 
receiver, in which is condensed a part of the water, of a 
second flask containing concentrated sulphuric acid which 
dries the gas and serves at the same time as a guide to the 
operator. By the rapidity of the bubbles which are given 
off he sees if it be necessary to quicken or retard the disen- 
gagement ; after leaving this vessel, the hydrogen gas tra- 
verses a tube full of chloride of calcium, from which it pas- 
ses into the iron vessel ; escaping from this it is conducted 
by a glass tube bent at a right angle and inserted beneath 
the surface of water in the receiver. To adapt the iron ves- 
sel easily to the other parts of the apparatus, we employed 
covers of iron which close it completely, and having in their 
centres iron tubes about 15 inches long. By means of this 
arrangement, the apparatus and iron vessel are heated to- 
gether, and the connexions are sufficiently distant from the 
fire not to be injured. 
We have said that it was necessary that the temperature 
should be sufficient, and that it should not be too elevated. 
We obtain a very convenient heat by the following dispo- 
sition : A small enclosure is made of a range of bricks placed 
on the ground : upon these bricks is placed an iron grating 
