106 CHEMICAL NOMENCLATURE AND NOTATION. 



Protoxide of iron, Fe 



Sulphuric acid, S 



Crystallized sulphate of protoxide of iron, Fe S, H + 6H 



Alum, K S, Al'Al S 3 + 24H 



Felspar, K Si, Al'Al Si 3 



Oxalate of peroxide of iron and potash, 3K CC + FeFe, 3CC -f 6H 

 Such formulae are more compact, and more easily compared 

 with each other, the relation between the mineral felspar and 

 alum without its water of crystallization, being seen at a glance 

 on thus placing their formulae together, the one having the 

 symbol for silicon, the other that for sulphur, but everything 

 else remaining the same. This abbreviated plan also exhibits 

 more distinctly the relation between the equivalents of oxygen 

 in the different constituents of a salt, which is always im- 

 portant. 



It is to be observed, that the oxygen expressed by the dots 

 placed over a letter is brought under the influence of the small 



figure attached to that letter, as for example, S 3 in the preced- 

 ing formula of alum, means three proportions of sulphuric 

 acid, so that this sign has the same value as if it were writ- 

 ten 38. 



Equivalents of sulphur are likewise sometimes expressed by 

 commas placed over other symbols, as the trito-sulphuret of 



arsenic by As, but such compounds are not of constant occur- 

 rence like the oxides, and do not create the same necessity for 

 any new and arbitrary symbol. A compound body, such as 

 cyanogen, which combines with a numerous series of other 

 bodies is often for brevity expressed by the initial letter of its 

 name, as 



Cyanogen . Cy, 



Benzoyle . Bz ; 



and the organic acids are sometimes expressed by a letter in the 

 same way, but with the minus sign ( ) placed over it, thus, 



Acetic acid, by A 



Tartaric acid, by T. 



But arbitrary characters of this kind will always be explained, 

 on the occasion of their introduction. 



