102 On Symbolic Notation, as applied to Mineralogy. 
published work on Mineralogy, with the formule by which 
the composition of such minerals is expressed. 
Hence arises the difficulty in selecting a chemical formula 
which shall accurately represent the chemical constitution of 
a mineral, and particularly as other symbolical expressions 
might, with a little contrivance, be framed to represent equally 
well the result of the same analysis. A question, therefore, 
occurs whether there is any rule to guide us in determining 
which formula is the most correct. 
The doctrine of definite proportions is, as I understand it, 
applicable to all cases of chemical union. An electro-positive 
and an electro-negative element are, in all cases, to be regarded 
as the combining atoms, whether such elements are simple, or 
consist of binary, quaternary, or any other compound of simple 
elements. Thus, one proportional of oxalic acid and one of 
potash are the combining atoms in oxalate of potash ; in binox- 
alate, two proportionals of the acid form the atom; and in qua- 
droxalate four proportionals. But in what manner do these 
two and four proportionals constitute the combining atoms? 
Again, in sulphate of nickel and potash, are the two elements 
sulphates; or is sulphuric acid one, and the combined oxides the 
other? And what function does the water perform in hydrous 
salts, as it does not appear in the formule representing such ? 
in what manner, or even whether it is combined with any, or 
which, of the elements of the compound in which it occurs ? 
On referring, however, to the last edition of Berzelius’s 
Theory of Chemical Proportions, I find that the inquiry I 
have thus ventured to suggest will probably not produce a sa- 
tisfactory answer; but as some chemists retain in their formule, 
and others reject, the same ingredient of a mineral, as shown 
by analysis, they perhaps have some rule by which they are 
guided, and which if worked out might furnish a clue to the 
object Iam seeking. The passage from Berzelius is as follows: 
¢ Sulphuric acid, potash, alumina, and water are compound 
atoms of the first order; sulphate of potash and sulphate of 
alumina are of the second order ; dry [anhydrous] alum, of the 
third order; and lastly, crystallized alum, containing water com- 
bined with the double sulphate, may be regarded as an atom of 
the fourth order. We are as yet ignorant of the extent of the 
number of these orders. Affinity among compound atoms de- 
creases rapidly as the numbers of the orders increase; and the 
degree which exists even among atoms of the ¢hird order is too 
feeble to be observed in the operations of the laboratory. This 
affinity is seldom manifested, except in minerals; and to un- 
derstand thoroughly the nature of these, it is necessary to know 
how far the combination of compound atoms can take place, 
