CARBON—LITTLE 245 
PLACE IN ORGANIC CHEMISTRY 
Carbon is the central element of the organic kingdom. It is 
closely related to life and to energy. Most of the energy for the 
world’s work in machine or animal or man is derived from the 
oxidation of carbon. Plants absorb carbon dioxide from the air to 
an estimated yearly amount of 13,000,000,000 tons and, under the 
stimulus of sunlight, fix the carbon in their structure in such com- 
pounds as cellulose, starch, and sugar. All vegetable and indirectly 
all animal life owes its existence, therefore, to the sun’s rays acting 
upon the carbon dioxide in the atmosphere. The initial step in this 
fixation of carbon is probably the transformation of carbon dioxide 
to formaldehyde through reaction with oxygen and hydrogen, the 
elements of water. As the result of this reaction plants exhale 
oxygen, whereas animals in a reverse process, as we have seen, 
exhale carbon dioxide. Bailey has recently synthesized glucose by 
subjecting formaldehyde to the ight of a mercury arc lamp. 
In comparison with all the other elements carbon is strikingly 
notable for the enormous number of its compounds. The known 
compounds of all the elements other than carbon are only about 
25,000, whereas the compounds of carbon reach the astonishing total 
of 200,000. This is due in large measure to the peculiar fact that 
the atoms of carbon exercise a powerful attraction for each other, 
by reason of which carbon compounds are built up which may con- 
tain many carbon atoms linked together in straight or branched 
chains, or in one or several rings, or in more complex configura- 
tions which include both chains and rings of carbon atoms in asso- 
ciation with those of other elements. Hydrogen is thus associated 
in the great majority of carbon compounds, which very often also 
contain oxygen. 
The amazing complexity of structure that carbon compounds may 
attain is indicated by the fact that compounds are known which 
have more than 200 carbon atoms in a single molecule, beside which 
a diagram of the solar system appears too simple to talk about. 
Organic chemistry, which is the chemistry of the compounds of 
carbon, is further complicated by the fact that many carbon com- 
pounds contain the same elements in the same proportions, but differ 
from one another in their properties. Thus 86 compounds of the 
formula C,,H,,.O, are known, and Cayley has calculated that 802 
of the formula C,,H,, are possible. Obviously, then, the properties 
of carbon compounds must depend not only upon the kind and 
numbers of atoms composing them, but also upon the manner of 
arrangement of these atoms within the structure of the molecule. 
Long-continued intensive study of the reactions of carbon 
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