C. G, Wheeler on a Process of Elementary Analysis. 87 
tion of the copper reduced. The same occurs also when the 
metallic copper at the anterior end of the tube is reached, at 
which stage of the process great care is necessary, for, as the 
oxydation of the copper commences, there is a sudden cessation 
in the passage of gas through the potash bulbs and one is easily 
tempted to accelerate the liberation of oxygen. In this event, 
when the reoxydation is completed, a very sudden and altogether 
too rapid stream of gas passes through the apparatus and disas- 
ter results. If, on the other hand, the liberation of oxygen be 
not sufficiently rapid, or, in particular, if it should cease for a 
few moments, the oxydation of the copper would proceed at such 
a rate and so reduce the tension of the gases within the appara- 
tus as to cause the mercury to ascend the tube communicating 
with the potash bulbs, and even to enter the latter if not timely 
observed and prevented by accelerating the stream of oxygen. 
€ one extreme, as well as the other, may be avoided by so 
regulating the stream of gas that constant but slow oxydation of 
the copper takes place, and this is readily seen by the change 
of color that results. Care should be taken that the necessar 
oxygen be liberated without interruption and uniformly, whic 
may be easily effected when the chlorate of potassa has been 
before weighin 
_ The height of the mercu ry in and surrounding the gasometer 
1s read off, after the same has been placed in an upright position 
in @ mercury trough with glass sides; also the height of barom- 
eter and thermometer. A portion of the gas is then transferred 
to the eudiometer, previously filled with mercury, in the follow- 
mg manner; the stopper of wax is removed from the extremity 
of the tube at ¢ and the latter is introduced into the eudiometer. 
The tube e is then inserted in the tubulure, and mercury is 
poured into the same until its level in the tube is above that in 
the gasometer by about one or two inches. The serew-clip at gis 
then gradually opened and the gas flows out through ¢ into the 
eudiometer, When enough has been transferred for an analysis, 
the serew-clip is closed, the gasometer removed and the amount _ 
Of gas in the eudiometer is read off, The further analysis of = 
the gas is performed precisely as in an ordinary air analysis” = 
? Bunsen’s Gasometrischen Methoden, p. 74. ees 
pelled by air previously freed from carbonic acid and moisture 
