The Determination of Sulfur in Rubber by Means of the Calorimetric Bomb

Abstract

Abstract For determining the total sulfur content of rubber, industrial laboratories ordinarily use some method which is based on the destruction of the organic substances, and oxidation of the sulfur to sulfur dioxide in an open vessel, e. g., by sodium peroxide, perchloric acid, or a potassium carbonate-potassium nitrate mixture. Particular attention should be called to the method of Butironi which is based on the fusion of the substance with dry potassium hydroxide in a silver crucible, and subsequent oxidation of the sulfur to sulfuric acid by potassium nitrate. This method can be used for hard rubber. There is also an interesting method of Losana, which involves heating the substance with powdered iron and sodium bicarbonate, treatment of the iron sulfide with hydrochloric acid, passage of the hydrogen sulfide into zinc acetate solution, addition of a known excess of iodine solution, and titration of the excess iodine. All these methods are tedious and delicate, and leave much to be desired from the point of view of precision because of losses through spattering or incomplete oxidation. Because of this, and because of the great simplicity and rapidity of execution with many organic substances other than rubber, the possibility of utilizing the calorimetric bomb for the determination of sulfur in rubber was investigated. Many tests on mineral oils and organic substances containing sulfur have proved the simplicity of the method and the certainty of perfect combustion and complete oxidation of the sulfur when the procedure is carried out with proper skill.