are involved, and the proportion produced in the pelt itself has a peculiar opening effect on the hide fibres. The activity of the drench can be decreased by dilution and by using a less starchy bran, and can be increased by adding pea meal or rye meal. Drenching usually follows bating. Scudding sometimes follows deliming.

The theory of the volume and elasticity changes of pelt during preparation will be better understood after considering the behaviour of gelatine gels (pp. 200-219). The determining factors are the nett charge of hydroxyl ions on the disperse phase, resulting from ionic adsorptions, and the lyotrope influence of dissolved substances on the continuous phase.

In softening dried hides the swelling may be due to either influence, but the latter tends to loss of hide substance and the production of soft leather.

In liming, the nett adsorption of hydroxyl ions is the principal factor, but the lyotrope influence of the alkali cations and of the impurities is important. Plump pelts are those in which the contained water is in a relatively greater average state of compression. Few substances can assist plumping, but many can hinder it. In plumping all lyotrope influence is objectionable, and "sharp" (pure) alkali solutions are required. Mellow limes reduce elasticity and plumpness by lyotrope influence.