On definite Proportions. 381 
104°], and weighed it from time to time, taking care to 
stir the powder. At the end of the time, it had assumed the 
form of a blackish brown powder, and had acquired -162 
gr. weight. The increase during “the last’? [a third?] 
month was only -0075 gr., and it then became sta- 
tionary. Consequently 100 parts of arsenic had united 
with 8°475 of oxygen; and this is so nearly } of the oxygen 
contained in the arseric acid, that the difference does not 
exceed half a thousandth of the weight of the protoxide ; 
so that we have hence a new proof that the multiples by 
14 are only apparent, and in reality represent multiples by 
6 or,12 of a smaller quantity. The protoxide of arsenic is 
reduced by heat, affording metallic arsenic and arsenious 
acid. 
VII. Tunestic AnD Motyspic Acips. 
Not having had an opportunity of making any original 
experiments on these acids, I shal] only calculate their com- 
position from the analyses of MM. Bucholz and Klap- 
roth. According to Klaproth (Beitr. ITI.47) 100 pnt of 
tungstate of lime afforded 32 of carbonate of lime and 
77°75 of tungstic acid. The 32 parts of carbonate of lime 
contain 18°05 of the earth, and in‘it 4°0719 of oxygen: 
this quantity, multiplied by 4, gives 16°287635 and if this is 
the quantity of oxygen contained in 77°75 of tungstic acid, 
this acid consists of 79°1 of metal and 20-9 of oxygen. 
Bucholz gives 80 and 20 for this proportion. 
In Klaproth’s analysis of the molybdate of the protoxids 
of lead (Beitr. 11.274) 100 grains were found to afford 744 
of the muriate, which contain 59°9 of the protoxide, with 
4*282 of oxygen, and 3 times this quantity gives 12°846. 
The salt of molybdzna afforded 34°25 of acid; and if this 
contained 12°846 of oxygen, the molybdic acid must con 
sist of 65°5 parts of metal and 34°5 of oxygen. According 
to the determination of Bucholz, it consists of 66°67 and 
33°33 respectively. 
The analyses, on which these two computations are 
founded, are not perfectly accurate; so that, notwithstand- 
ing the slight variation in the result, they serve as new and 
ample proofs of the law of nature which I have been endea- 
vouring to develop. 
Since all the acids, with the composition of which we are 
in any degree acquainted, follow the law which has been 
laid down, I think we are justified in applying the same 
mode of calculation to the investigation of the compositior® 
6f those acids also, which we cannot directly analyse. It 
‘ will 
