Experiments on the Electrodeposition of Rubber from Latex

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Abstract
Freshly tapped latex contains on the average from 27 to 35 per cent of rubber and from 1.2 to 1.7 per cent of acetone-soluble matter, such as resin and water-soluble sugars, from 1.5 to 2.0 per cent of protein and 0.25 to 0.20 per cent of mineral matter. The last consists mainly of the phosphates of calcium, magnesium, and potassium, with organic salts of these metals and a small amount of sulfate. Doubts have been expressed as to the existence of rubber as such in latex, since the physical properties of the dispersion bring it within the category of emulsions, i. e., of dispersions whose dispersed phase is liquid. Thus it has been suggested that the dispersed particles must consist of some simpler hydrocarbon which is polymerized to rubber during coagulation. From results obtained with the micro-manipulator, Freundlich and Hauser (Kolloid-Z., 36, 75 (1925)) concluded that the particles in latex consist of an elastic (solid) outer skin containing a viscous liquid, and assumed that the inner liquid hydrocarbon and the outer solid represent different stages of polymerization of the basic hydrocarbon isoprene C5H3. It is, of course, quite probable that the ejection of liquid which these investigators observed when a latex particle is punctured resulted from the rupture by the needle of the field of force at the surface of a liquid particle, and it is perhaps advisable to adhere to the more conservative conclusion of Stamberger (“The Colloid Chemistry of Rubber” (1929)) that in all raw rubber dispersions we are mainly concerned with liquid disperse phases. Latex is a relatively coarse dispersion with an average particle size of 0.5μ, and the particles vary in size from 2.0 to 0.1μ, i. e., from microscopic to ultra-microscopic particles (von Weimarn, Kolloid-Z., 46, 217 (1928)).

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