Among methods of concentrating rubber latex, the creaming process has, quite independently of the evaporation and centrifuge processes, aroused increasing interest because of its special technical features. The tendency of the rubber particles in latex to cream as a result of the difference in specifie gravity of the rubber and serum is a phenomenon which has been known for a long time. Hancock himself observed that when latex is stored, displacements in the concentration take place and he proposed to utilize this phenomenon in the preparation of very pure rubber particularly free of colored impurities. In 1824 Hancock suggested that rubber latex be diluted with water to one-fourth its concentration and the serum removed after a short period of standing. By repeating this process several times, a particularly pure product was said to result. In 1826 Faraday too described the same process. However, the displacements in concentration which become evident in latices which have stood for a long time without the addition of any creaming agent do not lead to any clearly defined layers. The first important observation on the spontaneous separation of two phases in latex by the addition of definite substances was by Traube. Among the substances described by Traube were colloidal mucilages such as gum tragacanth, soluble extract of Irish moss, etc.

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