V.—Expansion and Contraction of Coal caused respectively by the Sorption and Discharge of Gas

So far as we are aware, the only measurements that have been made of the linear extension of a colloidal medium due to gaseous sorption are those of Dr F. T. Meehan, published in 1927. Meehan studied the response of charcoal to carbon dioxide at atmospheric pressure and different temperatures, and found it to expand almost equally along and across the grain when it took in the gas. No tests of this kind appear to have been carried out with other rigid gels or with other gases, and none with any gas under pressure.