Professor DeebereinePs recent Discovery , to Eudiometry. 107 
that the atmospheric air contains either no hydrogen, or so very 
small a quantity as not to be rendered visible by the action of 
platinum. 
Different portions of oxygen were added to hydrogen gas, 
and the electric spark passed through the mixtures. When 9 
volumes of hydrogen were mixed with 1 of oxygen, electricity 
occasioned detonation ; but when they were mixed in the pro- 
portion of 11 to 1, a strong charge from a Leyden-jar caused 
neither detonation nor diminution. Platinum, however, caused 
immediate formation of water, and the quantity of oxygen was 
indicated by the diminution. 
I mixed 3 volumes of oxygen with 300 of hydrogen gas, with 
which a platinum-ball had been in contact for some hours. The 
ball No. 2., recently ignited, but quite cold, was put into 132 
volumes of this mixture. In half an hour there was a diminu- 
tion of 4 volumes, which indicates the presence of 1.3 oxygen, 
while 1.1 was the quantity present. The same ball was put into 
154 volumes of the same mixture- In half an hour there was a 
diminution of 5.5 volumes, which indicates 1.8 oxygen, while 
1.5 was the quantity present. 
Prom these experiments, it is apparent that the presence of 
hydrogen gas in oxygen or atmospheric air, or of oxygen gas 
in hydrogen, may be detected, and the exact quantity of either 
indicated by the action of platinum. It is clear, likewise, that 
analytical chemistry has hitherto possessed no agent of equal 
delicacy for these gases, and, therefore, that platinum may be 
used with great advantage in eudiometry. 
To put this conclusion to the test of experiment, I now pro- 
ceeded to an analysis of atmospheric air. A jar full of the air 
of my apartment was dried over mercury, and deprived of car- 
bonic acid by fused potash ; known quantities of this air, mixed 
with hydrogen, were exposed to the action of an active platinum- 
ball. 
1st Exp. The result was 21.8 of Oxygen per cent. 
2d Exp. 22.3 
3d Exp. 21,7 
The two first were performed in the narrow graduated tube, 
and lasted half an hour; the third was conducted in a capacious 
jar, and was over in five minutes. 
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