THE OLD AND THE NEW CHEMISTRY. 
27 
then we may write the formulae of these three bodies as C^H, 
C|H, and CH, or, to avoid fractional numbers, as CH 2 , C 2 H 3 , 
and CH respectively. But these formulae represent different 
volumes of the compounds. Let us take CH as the standard ; 
let the amount of this gas represented by this formula occupy 
1 volume, then the amount of the gas CH 2 represented by that 
formula occupies 2 volumes, the amount represented by C 2 H 3 
also occupies 2 volumes. 
Further, these equivalent formulae altogether fail to gene- 
ralize the reactions of the compounds which they represent. 
The old notation is said to be founded on facts and on facts 
alone. Numbers are attached to the elements representing the 
equivalents of these elements : the elements combine in the 
proportions expressed by these numbers, or by simple multiples 
of these numbers. But we have seen that to many elements 
1, 2, 3, 4 or more equivalents may be assigned ; which 
is the true equivalent? Further, we have seen that the old 
notation sometimes assigned an equivalent to an element which 
is really not the equivalent, not even an equivalent, of that 
element. The equivalent of nitrogen was said to be 14 ; but, 
as a matter of fact, 14 parts by weight of nitrogen are always 
found united with 3, not with 1 part by weight of hydrogen. 
The old notation made but little use of Gay Lussac’s great 
generalization concerning combination by volume. 
Lastly, the old notation very frequently failed, if rigidly 
carried out, to generalize the properties of the bodies to which 
it assigned formulae. 
I have shown that by adopting formulae representing the 
weights of two volumes of compounds, and by carefully analysing 
series of compounds, we arrive at certain numbers which ex- 
press the least (relative) amounts of the elements in the two 
volumes, and also the amounts of those elements which com- 
bine to form other compounds. 
So far we have made no use of the idea of equivalency. 
But when we come to compare together the amounts of the 
different elements represented by their combining numbers, as 
deduced by the process just mentioned, we find that, judged by 
a certain standard, these amounts sometimes are, and some- 
times are not, equivalent to each other. Thus, the combining 
number of carbon is 12, of oxygen 16, and of nitrogen 14. But 
12 parts by weight of carbon combine with 4 parts of hydrogen 
to form 2 volumes of a gaseous compound; 16 parts of oxygen 
combine with 2 parts of hydrogen to form 2 volumes of a 
gaseous compound ; and 14 parts of nitrogen combine with 3 
parts of hydrogen to form 2 volumes of a gaseous compound. 
Further, 2 x 1 6 = 32 parts of oxygen are capable of replacing 
the hydrogen in 2 volumes of the gaseous compound of carbon 
