Abstracts of Technical Articles from Bell System Sources (01 April 1938)

Elec. Engg., March 1938. Jour. S. M. P. E., January 1938. Phys. Rev., January 15, 1938. 319 320 BELL SYSTEM TECHNICAL JOURNAL Composition and Structure of Hevea Latex.* A. R. KEMP. Data and present views relating to the composition and structure of the latex particles are presented. The number of particles in one gram of 40 per cent latex was calculated to be 7.4 X 1012 on the basis that they have an average particle mass of 0.054 X 10-12 gram (from the microscopic data of F. F. Lucas, page 146). A study was made of the effect of several factors on the water content of rubber in pressed coagulum from fresh and treated latices. 

The average value for the water of retention of rubber coagula from fresh latex was found to be about 11 per cent, increasing to about 22 per cent in the case of old latex and deproteinized rubber from alkali-treated latex. This water appears to be held mechanically in the colloid hydrocarbon structure of the latex particles. The particle structure of sheet rubber is discussed and it is suggested that plasticization by milling involves the conversion of the gel hydrocarbon shell on the rubber particles to sol rubber through oxidation. Ultraviolet Microscopy of Hevea Rubber Latex.5 FRANCIS F . LUCAS. Samples of bulk rubber latex received in sealed cans from two sources have been investigated by means of the ultraviolet microscope. The advantages of the ultraviolet microscope are (a) an enormous increase in resolving power, (b) selective absorption of the ultraviolet light by many substances, and (c) the ability to section optically very small objects suited to the purpose.