Compounds cf Nitrogen. 505 
duced to the form of a rule, the new method 
may be stated as follows: Let a given volume 
of nitrous oxide be exploded with a slight 
excess of carbonic oxide of known purity ; for 
example, 110 or 115 measures of the latter 
to 100 of the former. Now as each volume 
of real nitrous oxide gives, under these cir- 
cumstances, an equal volume of carbonic 
acid, we may impute whatever carbonic 
acid is deficient of that proportion to the 
mixture of so much nitrogen with the nitrous 
oxide. If, for example, using an excess of 
carbonic oxide, there should result, from 100 
measures of nitrous oxide, only. 95 of car- 
bonic acid, we may safely consider the ni- 
trous oxide to be contaminated with 5 per 
cent of nitrogen gas. A proportion of nitrous 
gasmay, I am aware, be occasionally mixed 
with the nitrous oxide, but this may be easily 
discovered, and previously separated, by so- 
lution of green sulphate of iron. 
Having determined the application of car- 
bonic oxide to the analysis of nitrous oxide 
to be so easy and satisfactory, I had hoped 
that the same agent might have been employed 
in the analysis of nitrous gas, which, as is 
well known, does not form a combustible 
mixture with simple hydrogen gas.(e) But 
(c) Davy’s Researches, p. 136, 
3.8 
