252 Proceedings of the Royal Society of Edinburgh. [Sess. 
other hand, there are no instances contradictory of this point. Hence the circum- 
stance that it must ever remain impossible to isolate a combinate of the form C 2 H 3 
or C 4 H 5 , etc. 
Carbon having only two grades of combination of two atoms each, a fact which 
is easily traced throughout all organic chemistry, this inherent property of the 
element may legitimately furnish two grand types for all its combinates. 
The first type will be nC 2 M 4 . 
The second type will be nC 2 M 4 — mM 2 T 
As examples belonging to the first type, may be mentioned the alcohols of the 
sethylic form, their aethers, the fatty acids, etc. 
Thus methylic alcohol has the formula C 2 
... o • 0H 
H 3 
5 
and 
eethylic 
alcohol, 
"O ""OH 
; IT 2 
02-.-H 3 
In these instances it will lie observed, that for each double atom of carbon the 
combining power is (4) four, which is the ultimate limit of combination for carbon 
in all bodies yet produced. 
In the latter instance it is apparent, inasmuch as if the combining limit of two 
C 2 s be each reduced by 3 in hydrogen or oxygen, there still remains a combining 
power of one to each of the two C 2 s which each expends in uniting with the other ; 
C 2 -h 3 
therefore : , or, 
C 2 • H 3 
what is the same thing. 
™ ••()••• on 
C •• h 2 
belongs to the type nC 2 M 4 . 
C 2 • H 3 
Again, the inherent properties of the elements may be viewed as dividing bodies 
into primary, secondary, tertiary, and so on, combinates. These may be termed so 
many orders of complicity. Thus C 4 H 6 is a primary combinate, or it belongs to the 
first order of complicity ; but C 4 ....^ 5 is a secondary combinate, or belongs to 
the second order of complicity. C 2 0 2 and C 2 0 4 are primary, while C 2 0 4 , 20H and 
C 2 0 4 , 20Ka are secondary. 
A primary combinate is then nC 2 united to nM 4 or to nM 4 — mM 2 in such a 
* Misprinted “ mM ” in the original. 
