CHEMICAL NOTATION 
AND ATOMIC WEIGHTS. 531 
Former molecular weight New molecular weight 
Compounds. Density H = 1. 
and space occupied by 1 
molecule. 
and space occupied 
by 1 molecule. 
Ammonia .... 
8 53 
17, 2 vols. 
17, 2 vols. 
Water. 
9 
9, 1 vol. 
18, 2 vols. 
Hydrochloric Acid . 
17-98 
36-5, 2 vols. 
36 5, 2 vols. 
Sulphurous Acid Gas 
32-25 
32, 1 vol. 
64, 2 vols. 
Carbonic Oxide , . 
1395 
14, 1 vol. 
28, 2 vols. 
Carbonic Acid Gas . 
2205 
22 , 1 vol. 
44, 2 vols. 
Ether. 
37 29 
37, 1 vol. 
74, 2 vols. 
Calomel. 
118-55 
235"5, 2 vols. 
235 5, 2 vols. 
Corrosive sublimate. 
141-5 
135, 1 vol. 
271, 2 vols. 
The new molecular weights for these compounds are, therefore, just double 
their densities in the state of vapour referred to hydrogen as unity. 
In the law quoted above, the term molecule is made to apply to simple gases 
equally with compounds. The question then arises, what is to be understood 
by the molecule of an element? The reply is, that it is defined as the 
smallest quantity of an element which it is assumed can exist alone or uti- 
combined with other elements. If the molecules of the elements be repre¬ 
sented as consisting each of 2 atoms, one of these elementary molecules will, 
in the state of vapour, occupy the same space that the molecules of compound 
bodies do ; in other words, 2 volumes. 
Molecular weight, 
Hydrogen . 
Density. 
. 1 
= Density x 2 
2 
Formula. 
H 2 
Oxygen . . 
. 16 
32 
o 2 
Chlorine 
. 35 5 
71 
CL 
Bromine 
. 80 
160 
Br, 
Iodine . . 
. 127 
254 
1/ 
This idea is not merely fanciful, but receives some countenance from the 
chemical deportment of the elements. Every one is aware of the exalted ac¬ 
tivity displayed by most elements, their power of effecting decompositions, 
and of attaching themselves to other bodies, whilst in that peculiar condition 
known as the “ nascent ” state. Contrast, for example, the properties of 
hydrogen when at the moment it is set free from a state of combination, as by 
the action of zinc on dilute sulphuric acid, of sodium-amalgam on water, etc., 
and those which it presents after being collected in the ordinary way in bulk. 
The above hypothesis offers an explanation of the remarkable powers re¬ 
siding in nascent bodies. Gaseous hydrogen, oxygen, and the rest, are made 
up of molecules ; when the atoms are set at liberty, if there is nothing else 
present with which they can combine, they unite among themselves in pairs, 
and thus, as far as possible, mutually satisfy their affinities. In order to enter 
into new combinations, subsequently to this change, an already existing che¬ 
mical compound has thus to be torn asunder, and the elements in this mole¬ 
cular condition, therefore, exhibit a kind of languor in their reactions which 
is not the case whilst the atoms are yet distinct. But, it will be observed, 
this is only adding one hypothesis to another; some more direct and tangible 
evidence than this is necessary. Such, it is said, is to be found in those very 
extraordinary reactions in which two bodies, highly charged with oxygen, de¬ 
compose each other, and where it is impossible not to believe that the oxygen 
contained in the one has an affinity for that of the other. 
Chromic anhydride. Peroxide of Hydrogen. Oxide of Chromium. Water. Oxygen. 
2 Cr0 3 -j- 3H., Oo — Cr 2 0 :1 -f- 3H 2 0 -j- 30 2 
2 m 2 
