Contributions to the Analysis of Rubber. II. The Qualitative Determination of the Serum Components of Raw Rubber and of Vulcanized Rubber

The use of latex in the rubber industry has been increasing to a considerable extent, and in many cases where formerly solutions of ordinary plantation rubber were used exclusively, e. g., for impregnating fibres, spreading and adhering textiles, and manufacturing dipped goods, latex mixtures are now employed. Then again there is increasing interest in rubber prepared by evaporation or spraying of latex, especially for the production of powdered rubber. Consequently the time has come, as is evident from recent publications, when it may be an important problem whether in the preparation of a rubber mixture it is best to use ordinary plantation rubber, latex, or, perhaps, evaporated latex. Now the peculiarity of a rubber mixture prepared from latex or from evaporated latex is its relatively high precentage of serum substances from the latex. In the first Communication on the present subject, which dealt with the “Determination of the Water-Soluble Components of Rubber,” a method was described for determining the serum substances in vulcanized rubber. In view of the fact that with technical rubber mixtures, and in the presence of zinc, calcium, and magnesium compounds, this method is complicated and tedious, the present experiments were carried out with an aim to developing a procedure for determining qualitatively the serum substances. A method of this kind must naturally be restricted to the identification of some substance which originates in the serum and not in the curvatives or other compounding ingredients. Among the various substances which are present in latex serum, 1-methylinositol is one of the most important, and rubber mixtures prepared from latex or from evaporated latex contain a notable quantity of this substance. Consequently proof of the existence of 1-methylinositol in a mixture should be evidence of the presence of serum substances. The investigation to be described was therefore confined to the development of a characteristic reaction of 1-methylinositol.