Haughton — Notes on Newtonian Chemistry, 
635 
adding together, we find 
but, since C is the centre of gravity, I, m are inversely as a, /? ; 
therefore 
and 
^' = Z3(^^. (3) 
The molecular volume of a gas is measured by atomic weight 
divided by specific gravity, and the molecular volumes of hydrogen 
and chlorine, determined by the best experiments, are found to be. 
Molecular Volume. 
Hydrogen = ^^^^^ = 28-88 ; 
^ ^ 0-06926 
, . 2x35-5 „^ 
Chlorine = — — -r- = 28-89 ; 
2-45 
and the molecular volume of hydrochloric acid is known to be the 
same, by a comparison of its molecular weight with specific gravity : 
or, in other words, the number of molecules of hydrogen, of chlorine, 
or of hydrochloric acid, in a given volume, is the same, at equal 
pressures and temperatures. 
We must now define our units of space, time, and mass. 
I take for unit of space the radius of the orbital circle of the 
hydrogen or chlorine molecule, which must be equal to the radius 
of the orbit of hydrogen, in the hydrochloric acid molecule. 
The unit of time is defined by making w = 1 in the hydrogen mole- 
cule motion, and the unit of mass is given by making a = 1, which is 
the atomic weight of hydrogen. Equations (1), (2), (3) thus become 
= 4. (ly 
.'=^^'^ (3)' 
