238 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
that dense materials like nut shells yielded a superior charcoal, and 
peach stones and coconut shells became overnight munitions of the 
first importance. The porosity and adsorptive power of charcoal 
from such sources was further greatly increased by secondary or 
so-called activating treatments, and charcoals were finally produced 
of such efficiency that very high vacua are obtainable by their use. 
They may condense within their pores several hundred times their 
own volume of ammonia and lesser, though still large, amounts of 
the poison gases used in warfare. A good activated charcoal will, 
for example, absorb three-quarters of its weight of chloropicrin and 
will, in less than 0.03 second, reduce a concentration of 7,000 parts 
per million to less than one-half part in a rapidly moving stream of 
air. 
Such phenomena obviously mean that the adsorbed gases are held 
within the charcoal by the force of surface attraction under pres- 
sures equivalent to many tons per square inch and that they are in 
many cases condensed to liquid films. 
At the close of the war these properties of activated charcoal 
were immediately utilized by Colonel Burrell and others in the 
now well-known charcoal process for the extraction of gasoline from 
natural gas at the casing head, by which many million cubic feet 
of gas are now stripped daily, the adsorbed gasoline being recovered 
by heating the charcoal. 
GRAPHITE 
Graphite, so familiar to us all in the business end of a lead pencil, 
is another form of carbon for which many uses have been found. It 
occurs in nature, the best coming from Ceylon, where it is found in 
large, lustrous flakes, and it is artificially produced in quantity by 
heating coke or anthracite coal to high temperature in the electric 
furnace. It is several times as dense as charcoal and is a good con- 
ductor of electricity. As it is infusible and very inert chemically 
it is largely used for crucibles, and as it is also very smooth and soft 
it is commonly employed in facing molds in foundries and as a 
lubricant for heavy machinery. It lends its luster to the kitchen 
stove. 
DIAMONDS 
In the form of soot, carbon is black, amorphous, and synonymous 
with dirt and grime; as coke and charcoal, it is dull, porous, and 
readily combustible; as graphite, it is dense, lustrous, and so soft 
that it leaves a mark on paper. It is opaque in all these forms. But 
carbon in society has quite a different aspect from carbon in its work- 
ing clothes. There it is the diamond, transparent, sparkling, bril- 
lant with flashing color, and so intensely hard as to be well named 
in Greek ’A8dyas, the invincible. Confusion of this Greek name with 
