John Braithwaite Robertson

The Chemistry of Coal Volume 6 John Braithwaite Robertson

Publisher Marketing: This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ... the constituents of coal are soluble in strong oxidising agents such as potassium chlorate and hydrochloric acid, nitric acid, etc., there being formed either chlorinated or nitrated products of complex constitution and which are more or less typical of the coal used. The Destructive Distillation Of Coal. The destructive distillation of coal at ordinary pressures is a process of great technical importance, and the products obtained by this means are many and varied. Their nature casts a certain amount of light on the composition of coal, but the process of distillation takes place at a somewhat high temperature, and the decomposition is such that it is probably well within the mark to say that of the several hundred recognised products of distillation not more than a few of the gases evolved and of the simpler hydrocarbons exist as such in the coal before distillation. It has, however, been found possible, by means of carrying out the distillation in a vacuum or under reduced pressure, to isolate several constituents of coal in an unaltered form, and in other cases to obtain products much nearer to the original coal constituents than those obtained by distillation at ordinary pressures, and on which it is therefore possible to build up reasonable hypotheses as to the chemical nature of the coal substance or substances. Vacuum Tar.--Several experimenters have followed the procedure of first obtaining a "vacuum-tar" by distilling the coal under reduced pressure, and then 36 endeavouring by various means, such as the action of solvents or fractional distillation, to isolate constituents of this tar. The process presents many difficulties in practice. For instance, Pictet and Bouvier6 found that on fractionally distilling vacuum tar there...