The process of extraction with volatile solvents is similar to that used in the extraction of oils and fats, but as only the most highly purified solvents can be used, this process has not yet gained commercial importance.
Various solvents, such as benzene, alcohol and chloroform, will dissolve out the pigment, leaving the plastid colorless.
That nothing analogous to bitumen exists in coals is proved by the fact that the ordinary solvents for bituminous substances, such as bisulphide of carbon and benzol, have no effect upon them, as would be the case if they contained bitumen soluble in these re-agents.
Though his writings abound in universal solvents and other devices of the alchemists, he made some real contributions to chemical knowledge.
Certain solvents, such as water, liquid ammonia or liquid hydrocyanic acid, possess the power of making some solutes, such as mineral salts and acids, when dissolved in them, conductors of electricity.