288 Dr. Henry on the action of finely divided platinum on 
On calculating what should be the specific gravity of a 
mixture of gases in the above proportions, it was found to be 
•8°S>* which coincides, as nearly as can be expected, with the 
actual specific gravity of the gas submitted to analysis, viz. 
.308. To place the correctness of the results beyond ques- 
tion, I mingled the gases in the above proportions, and acted 
on the artificial mixture in the same manner as on the original 
gas, when 1 had the satisfaction to find that the analytical 
process again gave the true volumes with the most perfect 
correctness for the hydrogen and carbonic oxide, and within 
the fraction of a measure for the carburetted hydrogen. Not- 
withstanding this successful result, which was twice obtained, 
I should still prefer, for the reason which has been stated, 
having recourse to a temperature carefully regulated, for the 
analysis of similar mixtures, in all cases where the hydrogen 
is in moderate proportion, and where great accuracy is de- 
sirable. Whenever (it may again be remarked) olefiant gas 
is present in a mixture, it should always be removed by 
chlorine, before proceeding to expose the mixture to the 
agency of the spongy metal. 
It can scarcely be necessary to enter into further details 
respecting methods of analysis, the application of which to 
particular cases must be sufficiently obvious, from the experi- 
ments which have been described on artificial mixtures. The 
apparatus required is extremely simple, consisting, when the 
balls are employed, of graduated tubes of a diameter between 
0.3 and 0.6 of an inch ; or, when an increased temperature 
is used, of tubes bent into the shape of retorts, of a diameter 
* In this estimate, the specific gravity of hydrogen is taken at .0694 ; that of car- 
bonic oxide at .6722 ; of carburetted hydrogen at .5555 ; and of nitrogen at .9728. 
