Comperative i.r., ultimate analysis and yield of γ-fraction, pyridineor chloroform-extract from raw coal and coal preheaed at 250°C, 300°C, 350°C, 400°C, and 450°C have been examined respectively.
It was deduced that: (1) increase of extract from preheated coal is due to the exudation of bitumen from inside of coal, (2) the higher preheating temperature is, the more exudation of bitumen from occurs, (3) on the other hand, both of evaporation and thermal decomposition of extractive substance take place rapidly above 400°C of preheating temperature, (4) extract from coal preheated below 400°C scarcely contains the product of thermal decomposed coal, because i.r., ultimate analysis and yield of pyridine-extract or γ-frction and molecular weight of pyridine-extract from preheated coal are almost the same as those of corresponding extract from raw coal respectively.
From these deduction, it was infered that the maximum yield of chloroform extract at a certain temperature (for example 400°C) might appear by mutual relation between exudation and evaporation of chloroform-extract, and chloroform-extract from coal preheated below 400°C might be present in the raw coal as such.
