CHEMISTRY. 17 
amount of pure metal in a certain combination, such as the protoxyde or 
peroxyde. 
For this experiment we may use the apparatus represented in 
pl. 31, fig. 58. A glass tube, b, constructed of glass of difficult fusion, and 
having a bulb blown in the middle, has small brass cocks attached to each 
end by caoutchouc tubes. By means of these cocks the tube is to be 
attached to an air-pump, and afterwards weighed when all the air has been 
removed. Note must be taken of the loss of weight in the tube, produced 
by the exhaustion of the air. Into the bulb of the tube is now to be 
introduced a quantity of still hot oxyde of iron, heated over a Berzelius 
lamp. This lamp (fig. 11), one of the most convenient of all chemical 
apparatus, is constructed as follows: a is an annular vessel for containing 
alcohol, the space within the annulus being occupied by a cylinder, e¢, in 
communication with the vessel. The cylinder is double, one within the 
other: an annular bottom is soldered between the two cylinders, thus 
inclosing a space which is brought into communication with the space of 
the vessel a, by means of two short tubes passing between @ and c. A 
tubular lamp-wick is placed in this space between the two cylinders, and 
kept constantly moistened by the alcohol flowing from a through the tubes ; 
this wick may be regulated, as to height, by a screw, f. The space within 
the inner cylinder is open at both ends, thus allowing the introduction of a 
constant stream of fresh air into the centre of the wick when burning. 
The flame is surrounded by the small chimney g, made of sheet iron, and 
intended to increase the draught. The lower slide, d, of the stand, e, 
carries the lamp, and another above it the vessel to be heated, in this 
instance the crucible 6. Both slides may be set at any height along the 
vertical rod of the stand, by means of lightning-screws. The iron pincers 
( fig. 64) are used to handle the heated vessel. 
If now, as already mentioned, a sufficient quantity of oxyde of iron, as 
from thirty to fifty grains, be removed from the crucible into the tube 6 
( fig. 58), the oxyde of iron is to be permitted to cool in a vessel filled with 
dry air; the cocks are to be again attached, and the air pumped out, after 
which the tube is to be again weighed. The excess of weight in the latter 
weighing will represent the weight of the oxyde introduced. After again 
removing the cocks the glass tube is to be connected by dried cork or 
caoutchouc tubes, with the rest of the apparatus shown in fig. 58. Here 
Aisa gasometer filled with hydrogen; B a flask half full of sulphuric acid ; 
a a bulb tube containing chloride of calcium ; then comes the tube with the 
oxyde of iron, and to this succeeds the tube e, likewise filled with chloride 
of calcium. After this series of tubes has been connected air-tight by 
means of the glass conducting tubes, f, f, f, the cock, e, of the gasometer is 
to be opened. The hydrogen passes out in bubbles through the sulphuric 
acid into the top of B, thence through f into the first chloride of calcium 
tube a. The sulphuric acid through which the gas is driven abstracts from 
it the mingled watery vapor; this, however, is done more completely by 
the chloride of calcium, the gas arriving perfectly dry in the tube b, where 
it comes into contact with the oxyde of iron. As soon as all air in the 
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