320 Kremers—On the Classification of Carbon-Compounds. 
Since there is but one hydro-carbon, namely, methane, in which 
all four affinities of the carbon atom are saturated by hydrogen, 
its tetra-hydroxy derivative with its partial and complete anhy¬ 
drides will occupy a unique position in a system of classifica¬ 
tion of the oxygen derivatives of the paraffin hydro-carbons. 
For like reason we find among the nitrogen derivatives of 
this series of hydro-carbons several derivatives, which in a 
system of classification call for an isolated position, i. e., can¬ 
not be treated as members of series, since they do not form 
series of the kind under consideration. These compounds are 
/NH a 
carbon tetramine, C(NHo) 4 , guanidine, C=NH , carbon di-imine, 
x NH 2 
C CnH’ and cy anamide > C \NH 2 - Ifc wil1 readily be seen that 
the three first compounds may be likened to ortho-carbonic 
acid, meta-carbonic acid and carbonic acid anhydride, respec¬ 
tively. As a matter of fact, e. g. carbamic acid is stated to oc¬ 
cupy an intermediate position between meta-carbonic acid and 
urea: 
/OH 
c = o 
\OH 
V --- J 
Meta-carbonic 
acid. 
/OH 
c=o 
Carbamic 
acid. 
/NH 3 
C^O 
\NH 2 
/NHo 
C=NH 
\nh 2 
Urea. Guanidine. 
With the same propriety, urea can be considered as an inter¬ 
mediate product between carbamic acid and guanidine. 
The relations existing between alcohols, aldehydes, ketones, 
and acids are so generally understood, also the gradual change 
from the first to the last, or vice versa, that it is not at all 
necessary to comment on a system of classification of the 
hydroxy substitution products of the hydro-carbons and their 
partial and complete anhydrides based upon the theory of sub¬ 
stitution and subsequent dehydration. 
As to nitrogen derivatives, some further evidence than that 
already given may not be out of place. That ammonia splits 
off from numerous compounds containing nitrogen is a fact gen¬ 
erally known. The manufacture of ammonia from various sources 
is based upon this observation. The chemist studying amines, 
etc., has frequent occasion to deplore the instability of such 
