On definite Proportions. 247 
Secondly: with bases. Here the water takes the place of an 
acid, but contains only an equal quantity of oxygen with the base, 
or sometimes even a submultiple only. The water of crystalliza- 
tion is here again distinct from the water combined in the place 
of an acid. 
c. Combinations of alkalis, earths, and oxides, with each other 
in pairs. Although my experiments exhibit no example of such 
a combination, it is obvious that it must be classed in this place. 
For, whether we call the oxides of chromium, molybdenum, 
tungsten, tantalium, and tin, acids or oxides, the rule must be 
equally applicable to them, and that which is a law for one oxide 
must also hold good with respect to others. Besides, since such 
combinations of two bases are the foundations of double salts 
_ with double bases, and since the law prevails with respect to 
these salts, we may consider this as a sufficient proof of the ge- 
neral law. 
Combinations of two acids belong also here, for example, the 
fluoboric acid, in which the weaker acid probably occupies the 
place of a base, 
3. 
When three or more oxygenixed bodies unite with each other, 
the oxygen of the body which contains the smallest quantity 
is a common divisor, or rather an aliquot part of the oxygen of 
the others, each of which must therefore be an integral multiple 
of this smallest quantity. 
To this law belong :_ 
a. Salts containing water of crystallization. In the neutral 
salts the water of erystallization contains 1, 2,3,4,5.. times 
as much oxygen as the base, or more rarely 4, 4, } as much. 
In subsalts in which the oxygen of the acid is a submultiple of 
that of the base, the water of crystallization contains a quantity 
of oxygen which is a multiple of both the quantities, in the acid 
and in the base. 
b. Double salts. Examples of salts in which the oxygen of 
the one base is either equal to that of the other, or an integral 
multiple of it, are afforded respectively by the double salts of 
ammonia and magnesia, and by alum. When water of crystal- 
lization is present, the substance is a quadruple compound, and 
the oxygen of the component part, which contains the least of 
it, is a common divisor, or an aliquot part, of the oxygen of the 
others, as we have seen in alum, in which the oxygen of the po- 
tass is contained three times in the alumina, 12 times in the sul- 
phuric acid, and 24 times in the water. 
c. Combinations of several alkalis, earths, and oxides, in- 
cluding crystallized minerals. Although we are not authorized 
by 
