448 
Book I. 
Division II. 
Number of 
metallic 
aats. 
SALTS. 
one metallic salt into another—were so many anoma 
lies which rémained long inexplicable : But they were 
of too interesting a nature not to excite attention ; and 
to the successive researches of chemists into the pro 
perties of metallic salts must be ascribed a great part 
of the progress which chemistry has made. Many ap 
parent anomalies have been happily explained by the 
successive labours of Bergman, Scheelé, Bayen, Lavoi 
sier, Proust, &c. ; but there still remain a sufficient 
number of difficulties in this part of this science to ex 
ercise the sagacity of the most acute philosophers, and 
discoveries to be made in it which will fully compen 
sate the most laborious investigation. 
As there are 21 metallic bases from which these bo 
dies derive their chatacteristic properties, this class of 
salts may be divided into 21 genera. Since there are 
32 acids with which each base has to combine, it would 
seem at first sight that the number of species belong 
ing to each genus ought to amount to 32, which would 
make the metallic salts amount in all to 672. But it is 
not the metals which combine with acids, it is their 
oxides, or the compounds which they form with oxy 
gen : the metals themselves, as far as is known at 
present, are not capable of combining with any acid. 
Now as most metals form more than one oxide, and as 
each of the oxides of a metal is often capable of combi 
ning with acids, it is evident that the number of me 
tallic salts must greatly exceed 672. Thus iron being 
capable of forming two oxides, the species of salts of 
iron, instead of 32, must amount to 64, provided each 
of these oxides be capable of combining with all acids : 
the contrary of which has not been proved. 
It has been shown formerly that the difference be¬