ON CHEMICAL SYMBOLS. 
103 
stitution may be made in the formulae of the primary com- 
pounds; but the + must be retained as a connection between 
these compounds, and when the formula is thus modified 
the parentheses are not necessary; thus, KO.S0 3 + APO 3 . 3S0 3 . 
The figures used to denote the multiplication of the elements 
or their compounds, differ in their effect according to the 
position which they may occupy in the formula, and have 
sometimes an intimate relation with the sign -f- or its sub- 
stitutes. A number in a formula on a level with the line, 
multiplies all the symbols that follow to the first sign -f or 
full stop which occurs; or if these do not occur, its force con- 
tinues to the end of the formula. The only exception is, 
when the number is prefixed to formula3 enclosed in parenthe- 
ses; the whole thus enclosed is then affected by it. But when 
it is placed after and at the top of the symbol, the effect is dif- 
ferent. The element immediately preceding is alone mul- 
tiplied, when all the elements are expressed by symbols; but 
when the doubling of the radical or the equivalents of oxygen, 
&c, are denoted by signs, then the whole formula is under 
its influence, the effect being the same as if the number had 
been prefixed; thus 2Fe and Fe 2 , each denote two equivalents 
of sesquioxide of iron. 
As the principles derived from the animal and vegetable 
kingdoms, when resolved into their ultimate constituents, are 
found to consist of from two to four elements united in differ- 
ent proportions, it becomes burthensome to the memory to 
recollect, and inconvenient in practice to express by regular 
formulae, the varied composition of these substances. Some 
concise mode of denoting the compounds is, therefore, desir- 
able. So far as organic acids are concerned, Berzelius 
designates them by arbitrary symbols formed from the initial 
letter of the acids, in the same way as the symbols of the 
elementary bodies are formed, and, to distinguish them, 
places a dash over the symbol; thus acetic acid is expressed 
by A, instead of the formula C 4 H 3 3 ; benzoic acid by B, in- 
stead of C 14 H 5 3 ; citric acid by C, instead of C 4 H 5 4 , &c, 
