We have not space to treat fully of the proceedings
of the Congress of Applied Chemistry, but may briefly notice one paper of great practical interest read in the Hygienic Section on Monday. The author, Dr. Grossmann, of Manchester, dealt with the rational disposal of sewage sludge, which at present, after filtration, is dumped down on land specially bought for the purpose, rendering it unfit for any other use,—owing to the presence of a large amount of grease and soap. By the process devised by Dr. Grossmann, and now carried out at the experimental works installed by the Oldham Corporation, sludge-cake is dried by heat, mixed with a little acid, and passed through a specially designed retort, in which it is subjected to a current of superheated steam. In this way the steario skid, a valuable article of commerce, is carried off and recovered, while the residue, which is of great value as manure, is completely sterilised in the form of an odourless dry powder, and can be stored or used on land without creating a nuisance. As it is computed that four hundred thousand tons of soap are used every year in this country, practically all of which finds its way into the sewage, and in view of the fact that in many places the time is rapidly approaching when no further dumping-ground can be obtained in the neighbourhood of sewage-works, the practical advantages of the process, assuming that it effects all that is claimed for it, cannot be easily exaggerated.
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