It has been pointed out that the first charcoal was made from red cedar. While this was very satisfactory when tested against chlorine, it was of no value against chloropicrin. In order to improve the charcoal still further it was desirable to have some theory as to the way charcoal acted. It was generally agreed that fine pores were essential. The functioning of charcoal depends upon its adsorptive power and this in turn upon its porosity. The greater the ratio of its surface to its mass, that is, the more highly developed and fine grained its porosity, the greater its value. Another factor, however, seemed to play a rôle. As a pure hypothesis, at first, Chaney assumed that an active charcoal could only be secured by removing the hydrocarbon which he assumed to be present after carbonization. Being difficultly volatile, these hydrocarbons prevent the adsorption of other gases or vapors on the active material. To prove this, red cedar charcoal was heated in a bomb connected with a pump which drew air through the bomb. Although the charcoal had been carbonized at 800°, various gases and vapor began to come off at 300°, and when cooled, condensed to crystalline plates. This experiment not only proved the existence of components containing hydrogen in the charcoal, but also showed that one way of removing the hydrocarbon film on the active carbon was to treat with an oxidizing agent. In the light of the later experimental work Chaney feels that there are two forms of elementary carbon—“active” and “inactive”; the active form is characterized by a high specific adsorptive capacity for gas while the inactive form lacks this property. In general the temperature of formation of the active form is below 500-600° C. The form is easily attacked by oxidizing agents—while the latter is relatively stable. The combination of active carbon with an adsorbed layer or layers of hydrocarbon is known as “primary” carbon. Anthracite and bituminous coal are native primary carbons, while coke contains a considerable amount of inactive carbon, resulting from the decomposition of hydrocarbon during its preparation. PREPARATION OF ACTIVE CHARCOAL “On the basis of the above discussion, the preparation of active charcoal will evidently involve two steps: “First.—The formation of a porous, amorphous base carbon at a relatively low temperature. “Second.—The removal of the adsorbed hydrocarbons from the primary carbon, and the increase of its porosity.