IN GASES: HYDROGEN, CARBONIC OXIDE, AND OXYGEN. <523 
used is as small as possible, and the mixture therefore approaches the limit of inflam¬ 
mability. As the quantity of oxygen is increased, he says, the proportion of steam 
to carbonic acid produced must necessarily approximate to the proportion in which 
the hydrogen and carbonic oxide are originally present, although this proportion is 
never actually reached, because, when the oxygen is nearly sufficient for complete 
combustion, the hydrogen is all burnt while some carbonic oxide remains unoxidized. 
The true coefficient of affinity, according to v. Meyer, is that obtained with the 
minimum quantity of oxygen. 
There is an obvious objection to this use of the term “coefficient of affinity.” The 
smallest proportion of oxygen used by v. Meyer was that which was just necessary 
to produce an explosion. He gives no proof that, if this proportion were diminished 
still further, the ratio of carbonic acid to steam produced would be unaltered. The limit 
of inflammability is not necessarily the limit of the exercise of chemical affinity. If 
we assume that oxygen unites with the excess of carbonic oxide and hydrogen accord¬ 
ing to the equations— 
2C0 + 0 3 =2C0 3 
2H 3 +0 3 = 2H 3 0 
then the divison of the oxygen between the carbonic oxide and the hydrogen depends 
on the rate at which oxygen unites with carbonic oxide, and the rate at which it unites 
with hydrogen, under the conditions existing at each moment from the beginning of 
the change until the last molecule of oxygen is broken up. These conditions change 
at each moment (without reference to the changes of temperature and pressure), since 
the carbonic oxide and the hydrogen are attacked at unequal rates, and therefore the 
proportions of carbonic oxide and hydrogen remaining unconsumed vary continually 
during the combustion. In this case, the final division of the oxygen represents the 
sum or net result of its dividing itself between the two combustible gases in a series 
of different ratios during a series of successive moments. Its division would represent 
the actual ratio of two constant rates only if one of two conditions were fulfilled. 
First, if the ratio of the combustible gases in the original mixture were the same as the 
ratio of carbonic acid and steam formed ; or, secondly, if the proportion of oxygen were 
so small that the subtraction, by combustion, of the corresponding quantities of the 
combustible gases would not materially alter their ratio. The first condition can only 
be fulfilled by burning all the combustible gases. The second involves the measure¬ 
ments of such small quantities that the errors of experiment become important. 
Practically, the limit of inflammability of the mixture imposes an inferior limit to the 
reduction of the quantity of oxygen which prevents the second condition being 
fulfilled. 
The effect produced by the presence of an inert gas, nitrogen, which takes no part 
in the chemical action, on the division of the oxygen between the two combustible 
gases was also studied by v. Meyer. He found that on addition of nitrogen the 
