Determination of Total Sulfur in Rubber and Rubberlike Materials

Abstract

Abstract The determination of total or combined sulfur in vulcanized rubber and materials of similar type involves numerous difficulties. This fact is attested by the very large number of methods which have been proposed. All the most important methods involve oxidation of the sulfur, in whatever form it may be present, to sulfate and weighing the latter as barium sulfate. The only essential differences lie in the methods of oxidation employed. The methods which seem to be the most popular at the present time are (1) oxidation of the sample in a Parr bomb with sodium peroxide, potassium chlorate, and sugar; (2) oxidation with perchloric acid and nitric acid, sometimes with the additional use of bromine; (3) oxidation with nitric acid and bromine, followed by sodium carbonate-potassium nitrate fusion; and (4) oxidation with nitric acid-zinc oxide mixture, bromine, and potassium chlorate. Serious explosions have been known to occur with perchloric acid oxidations; hence this method is not so popular at present as the other three. The fusion methods are reliable, but they are time-consuming and therefore not convenient when large numbers of samples must be handled.