CHEMICAL NOTATION AND ATOMIC WEIGHTS. 
9 
(SO,)" 
KH 
(SO,") 
o. 
Acid Sulphate of Potassium 
(SO ") 'f 
Sulphate of Sodium and Ammonium . ^ ^ j 0 2 
Sulphate of Zinc.^Zn"^ } ^> 2 
Ferrous Sulphate.} O 2 
Ferric Sulphate.^Fe^) v ^}^ 6 
Turpith Mineral.(SCX)"}^ 4 
All these are said to be type formulae, since they preserve a resemblance to 
that of the type ^ j O, and serve to recall the analogy existing between the 
reactions of that body and the compounds thus represented. 
Some chemists go further than this, and regard a chemical formula as a 
sort of chart, which is supposed to be capable of showing the directions of the 
imaginary “links” or “bonds” which hold the parts of the molecule 
together. “ It is no longer a question of classifying reactions ; the question 
is to determine the intimate structure of the molecule, by establishing the 
manner in which the atoms are bound together. Our rational formulae, then, 
do not now represent types of double decomposition; they have for their 
object to indicate the bonds which exist between the various atoms consti¬ 
tuting a molecule.” 
Water, to take an instance, is represented by a formula similar to that 
already employed, but possessing a different significance. By the expression 
0 [git is not now intended solely to indicate ‘that the two atoms of hydro¬ 
gen are separately capable of replacement, but to show that one atom is 
connected with one of the two bonds which the oxygen has at its disposal, 
the second of which serving for the attachment of the remaining atom of 
hydrogen. 
Again, methylic alcohol would now be written upon the same principles, 
CH, 
O 
H 
or 
C 
(OH 
either of which formulae expresses the same idea. That is to say, the first im¬ 
plies that the lower atom of hydrogen is connected with the group above by 
the mediation of the atom of oxygen which brackets them together: in both, 
three out of the four bonds possessed by the carbon are satisfied by H 3 , the 
remaining bond connecting this C with the oxygen, which, in ite turn, dispose 
of half its affinity in favour of the carbon, and half to the hydrogen adjacent 
to itself. The promulgators of these views have invented a system of graphic 
notation, by which they endeavour to give greater precision to their sym¬ 
bolic language. This graphic notation has assumed various forms ; that most 
commonly adopted in this country consists in the employment of circles to 
denote the various atoms, having attached to them arms corresponding in 
number with the units of affinity manifested by the element. 
Monatomic elements are known thus (^)— ; diatomic elements, 
triatomic elements, 
-O 
; etc., according to the atomicity, and these are 
combined together into diagrams in the manner shown in the following for¬ 
mulae, which express the constitution of:— 
