Variation in the Composition and Properties of Fresh Latex. And Subsequent Changes on Ammoniation

Abstract

Abstract Systematic examination has been made of 163 samples of latex drawn at the approximate rate of three per week over a period of fourteen months from a single tapper's task on old seedling trees, newly opened after several years' rest on the continuous alternate daily system. The latex samples were all examined, both in the fresh condition and after 10 days and 15 days preservation with 0.7% ammonia; during the last eight months certain tests were also made on the latex immediately after ammoniation on the day of collection. The tests included dry rubber content, total solids, acetone extract and acid number of whole-latex rubber films, surface tension, viscosity, stirring stability and ease of creaming. It has been observed that: (1) The difference between percentage total solids and percentage dry rubber content is greater after 10 days' preservation than in the fresh condition. (2) The acetone extract and its acid number from whole-latex film are less in freshly-ammoniated latex than in fresh latex, and very much greater in ammoniated latex stored for 10 days. The acid number after 10 days preservation is usually about twice that of the fresh latex. These findings and their implications are discussed in the text, in which experimental figures are given. High dry rubber content usually connotes low acetone extract and acid value in the fresh latex. (3) Values for surface tension before and after ammoniation are given. The fall in surface tension as a result of ammoniation has not been proven to be governed by the changes in acetone-soluble material, or the acid number thereof. (4) The viscosity of ammoniated latex is shown to be very significantly correlated with its dry rubber content. In the case of fresh latex the degree of correlation is much less; a possible reason for this is advanced. Experimental results are given. (5) The initial stirring stability is shown to be influenced by the initial dry rubber content of the latex. The data do not provide an adequate explanation of the changes in stability which take place on storage. (6) The creaming ease of new latex appears also to be influenced by its initial dry rubber content, but the present data are not adequate fully to explain the variations which are noted.