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Methods are described for the mutual separation and identification of six alkyl-substituted dithiocarbamates by ehromatography of their brown copper complexes on silica gel. These methods have been successfully applied to the detection of dithiocarbamates in vulcanized rubbers, and they form an extension to the scheme for the chromatographic identification of accelerators and antioxidants reported in a previous communication.

The chromatographic behavior on silica gel/Celite adsorbent, of thirty-two accelerators and antioxidants has been investigated. Adsorption series have been established with four binary solvent mixtures and, based on these results, some simple and rapid methods have been designed for the identification of the compounds. These depend on the application of various streak reagents to the extruded chromatographic column, and with many of the compounds they give an almost unambiguous identification, even when several compounds are present in admixture. The methods are discussed in relation to those previously available for the identification of accelerators and antioxidants. They offer some important advantages. The methods have been successfully applied to a number of rubbers of known composition. Accelerator transformation products have in some cases been detected or identified. No case of accelerator decomposition during chromatography has been observed, but decomposition of certain accelerators during acetone extraction of the rubber has been noted. The results obtained have been compared with previous work on accelerator transformation products.

C. FELDMAN1,2 has recently described a solution spark technique, wherein the solution under investigation is carried in an upper electrode consisting of a narrow graphite cup which has a porous base permeable to the solution, the lower electrode being a solid graphite rod.