ON THE REDUCTION OP IRON BY HYDROGEN. 
heating the oxide of iron during the passage of the gas 
and in contact with its particles. 
1st. Instead of the flask used by the chemists above- 
named, and which cannot be well regulated, I have used a 
self-regulating gasometer, a b, which has several advantages. 
Though best made of lead, yet for practical purposes it may 
be constructed of two kegs, one small enough to slip within 
the other, with tight joints. The smaller keg which replaces 
the leaden vessel b has its open end downward, and into the 
centre of its head a gas stop-cock is screwed, opening into 
its interior, and which constitutes the exit for the gas gene- 
rated within , over which control is given by the cock. As a 
much larger quantity of hydrogen is consumed than is requi- 
site to combine with the oxygen of the oxide, the amount 
of zinc used is proportionally great. The solution of two 
pounds of zinc in diluted sulphuric acid will yield about as 
much hydrogen as is requisite to deoxidize the same weight 
of sub-carbonate of iron, but in practice three or four times 
this amount will be required, as especially towards the last 
of the process a large amount of gas passes unused. About 
6 lbs. of zinc scraps and 8 lbs. of oil of vitriol diluted with six 
times its bulk of water, are the proportions best adapted for 
decomposing two pounds of the sub-carbonate of iron. 
2d. The jars i, c, which should be of three or four quarts ca- 
pacity, contain water and lime; i is half- filled with water, and 
is connected with the stop-cock of the gas generator by a 
leaden tube which dips below the surface of the water. An- 
other tube connects i with the jar c filled three-fourths full 
of fragments of unslaked lime, and reaches nearly to its bot- 
tom. A third tube connects c with the end of the reduction 
tube which passes through the furnace d, and a section of 
which is represented at /, g, h* 
3d. The reduction tube that I have employed is made of 
wrought iron, is thirty inches long and four in diameter. One 
end is open, the other closed, with the exception of an orifice 
of one inch in diameter into which an iron tube 12 inches 
