246 W. Gibbs on the Atomic Weights of Elements. 
Art. XXII.—Remarks on the Atomic Weights of the Hlemenis ; 
by Wotcorr Grszs, M.D., Prof. of Chemistry and Physics in 
the Free Academy in New York. 
In the present communication I shall endeavor to show that 
if the atomic weights of oxygen, sulphur and carbon are taken, 
respectively, as 16, 82 and 12, those of a majority of the other 
elements must be doubled. Ido not at present adopt the view in 
question; my object is simply to point out the logical consistency 
of the change. For the sake of convenience and precision of 
language I shall employ the terms atom, molecule and equiva 
lent, in the sense in which they are understood by the chemists 
of the new or unitary school.* An atom of any element is the 
least quantity of that element which can exist in combination: 
a molecule is the least quantity which can exist in the free state. — 
The definitions of atomic and molecular weights flow at once 
from those of atom and molecule. The equivalents of bodies 
are the relative quantities which replace each other in actual or 
ideal substitutions; they may correspond to atoms or to mole- 
cules, or may bear a simple numerical relation to either of these. 
The atomic weights of carbon, oxygen and sulphur are now gen 
erally considered — respectively 12, 16 suit 32, chiefly upon 
organic compounds, independently of any assumption as 1 
po Hiker the number of atoms of carbon, oxygen and 
phur is always even. : 
3. en oxygen or sulphur replace hydrogen in organle 
compounds, 2 units of weight of hydrogen are replaced by 16 
of oxygen or 82 of sulphur; 4 units of hydrogen by 32 of oxy- 
gen, and so on; in no case is one unit of weight of hydroge? 
replaced by 8 of oxygen. 
4. The least quantity of oxygen or sulphur set free in 9Y 
reaction is either 32 or 64, or is some multiple of 32 or 64. 3 
like manner the least quantity of oxygen or sulphur which 
reacts with any compound body is.a multiple of 16 or 82 by 
even number. 
The assumption is now generally made that the molecules of 
all substances in the gaseous state occupy the same volume: 
* See for example Kekulé, Lehrbuch der Organischen Chemie, i, 97, Erlangen, 1859 
