on the Origin of the Doctrine of Definite Proportions, Sc. 403 
intermediate state. The cause of this I have already attempted 
to demonstrate. Metals will unite to oxygen in various propor- 
tions until they are saturated. If 100 grains of a metal are only 
capable of uniting to fifteen grains of oxygen, they will attract 
and retain five grains with greater force than ten, and ten grains 
with greater force than fifteen*.” 
In the foregoing example I made use of the numbers 5, 10, 15, 
the two latter of which being multiples of the former, in order 
to the establishment of the principles of definite proportions, and 
it accords with many similar examples in my Comparative View. 
Dr. Murray, in treating on those principles, which originated 
with me, does not take the smallest notice of the source whence 
he derived his information, although in his explanation he makes 
use of nearly the same words, as the following short extract 
taken from his chapter on chemical attraction will show. ‘ If 
100 parts of a metal combine in one combination with ten of 
oxygen, and in another combination with twenty of oxygen, ten 
parts of oxygen in the latter compound will be easily abstracted, 
while the other ten parts, or that proportion which constitutes 
the first compound, will be retained with a much more powerful 
force. Sulphur combines with two proportions of oxygen; the 
larger proportion which exists in one of these is easily abstracted, 
while the entire quantity is abstracted with more. difficulty. 
Charcoal and oxygen afford a similar example ¢.”” So he goes 
on. Were J to comment on the foregoing circumstances as they 
deserve, it would be too severe; therefore | leave my readers to 
judge for themselves, and I have not the smallest doubt but they 
will feel as I do at this present moment. 
Having demonstrated by means of diagrams and numbers the 
laws by which certain metals precipitate others in their metallic 
state from solution in acidst, I next proceeded to the cause of 
some metals precipitating others in the state of oxides. ‘ Let 
us suppose 100 grains of tim when in perfect solution in acids, to 
be united to 15 grains of oxygen with the force of 5°5. Let 
iron attract oxygen with the force of seven, and let us suppose 
this force of the zon to be reduced to six by the accession of 
7:5 grains of oxygen § taken from the fim, and the attraction of 
the ¢in to the remaining oxygen to be increased by the abstrae- 
tion of this quantity of oxygen: in this case won cannot preci- 
pitate ¢in in its metallic state, although it may have greater at- 
traction to oxygen than the ¢7z has. Hence it is evident that a 
* Comp. View, pages 274, 275, + Page 77. t Ib. from page 262 
to page 273. 
§ Here again the numbers chosen are 7, 5 and 15, the latter being a mul- 
tiple of the former; this cannot be supposed to be mere chance. 
Cc2 metal 
