EUDIOMETERY. 
phate of iron, is indeed the one which is 
most liable to fallacy. The analysis of the 
air in the upper regions of the atmosphere, 
has since been executed with accuracy by 
Gay Lussac, assisted by Thenard. A glass 
balloon was filled with air, at the height of 
21,735 feet from the surface, the greatest 
which has yet been reached, and when 
opened under water by Gay Lussac after 
his descent, one half of its capacity was 
filled by the water, a sufficient proof that 
it had been accurately closed. The air 
was subjected to trial, both by Volta’s eu- 
diometer, and by the solution of sulphuret 
of potash ; it afforded by the former me- 
thod 21.49 of oxygen, in 100 ; by the latter 
21.63. Atmospheric air at the surface, ana- 
lysed at the same time in the eudiometer of 
Volta, gave precisely the same result, 21.49. 
(Nicholson’s Journal, vol. x. p. 286). 
Saussure, junior, also found, that the air 
on the summit of the Col-du-Geant con- 
tained within one-hundredth part as much 
oxygen as that on the plain, and even this 
difference may be ascribed to the difficulty 
of making the experiment with perfect ac- 
curacy. The uniformity of the composition 
of the atmosphere at different parts of the 
earth’s surface, appears also to be esta- 
blished. 
Mr. Cavendish originally observed, that 
air subjected to examination at different 
times, and air likewise from different places, 
was of perfectly similar composition ; (Phi- 
losophical Transactions, vol. lxxiii. p. 129) 
and the same observation had been made 
by Fontana, from his own experiments. 
(Philosophical Transactions, vol. Ixix.) 
Mr. Davy states, that no sensible dif- ' 
ference was found in the air sent from the 
coast of Guinea, and the air in England. 
(Journal of the Royal Institution, vol. i. 
p. 48). 
Berthollet found, that the air in Egypt 
and in France was similar, affording 22 of 
oxygen in the 100, any difference observed 
not amounting to a , two-hundredth part of 
the air submitted to trial. (Memoirs rela- 
tive to Egypt, p. 326). 
De Marti, by experiments in Spain, ob- 
tained the same uniformity of composition 
between 21 and 20 of oxygen in the hun- 
dred parts) in the air at places at a distance 
from each other ; and he adds also, as esta- 
blished by his experiments, that in every 
state of the atmosphere,whether with regard 
to temperature, to pressure, as indicated by 
the barometer, to winds, to humidity, to 
the season of the year, or the hour of the 
day dr night, the results Were precisely the 
same. (Journal de Physique, t. iii. p. 173). 
And more lately the researches of Hum- 
boldt and Gay Lussac, made with the view 
of determining this question, have establish- 
the same conclusion. (Journal de Physique, 
t. lx. p. 152). 
The instruments for subjecting atmosphe- 
ric air to such changes as may indicate its 
proportion of oxygen, have been called eu- 
diometers. When a mixture of nitrous gas 
is to be made with atmospheric air, the 
most convenient apparatus consists in a 
glass tube closed at top, and graduated by 
a diamond into cubic inches and parts. 
The lower aperture may be widened, in or- 
der that the gases may more easily be pass- 
ed up, and likewise to afford the facility of 
its standing alone upon the pneumatic shelf. 
It is likewise usual and advantageous to fit 
a stopper in the mouth by grinding ; a cu- 
bic inch measure will be required for deter- 
mining the quantities poured up. A bottle 
will do for this purpose, and the instrument 
may be made very well by a chemist who 
is obliged to work for himself ; by taking 
any small bottle whatever, and pouring its 
contents of water, by successive times, into 
the tube placed mouth upwards. By this 
means he will obtain a graduation, which, 
whether of the cubic inch or not, will an- 
swer the purposes of eudiometry. 
When air is to be exposed to a liquid sul- 
phuret, which absorbs the oxygen, the eu- 
diometric tube may be immersed in the li- 
quid. Professor Hope, of Edinburgh, has 
contrived a very simple, elegant, and accu- 
rate apparatus for this purpose, announced 
in “ Nicholson’s Journal,” iv. 210. It con- 
sists of a small bottle, of the contents of 
about three ounces, intended to contain the 
eudiometric liquid ; into the neck a tube is 
accurately fitted by grinding, which holds 
precisely a cubic inch, and is divided into 
a hundred equal parts, and on one side the 
bottle, near its bottom, there is a neck into 
which a stopper is ground in the usual man- 
ner. In the use of this apparatus, the bot- 
tle is first filled with the liquid employed, 
which is best prepared by boiling a mixture 
of quick lime and sulphur with water, filter- 
ing the solution, and agitating it for some 
time in a bottle half filled with common air. 
The tube, filled with the gas under exami- 
nation, or with common air, if that be the 
subject of the experiment, is next put into 
its place, and, on inverting the instrument, 
the gas ascends into the bottle, where it is 
brought extensively into contact with the 
