TITTLE AND ISAACS: SULPHUR IN RUBBER 235 



PHYSICS. — A study of some recent methods for the determination 

 of total sulphur in rubber.^ J. B. Tuttle and A. Isaacs, 

 Bureau of Standards. 



This investigation was undertaken to learn whetiier or not 

 the methods recently published for the determination of sulphur 

 in rubber were any improvement over the Waters and Tuttle 

 method, the one now in use at the Bureau of Standards. The 

 methods investigated were those of Spence and Young; of 

 Deussen, of Alexander, of the Joint Rubber Insulation Com- 

 mittee, of Kaye and Sharp; of Frank and Marckwald, and of 

 Waters and Tuttle. These were subdivided, according to the 

 method of attack, into three classes: direct solution, direct 

 fusion, and solution and fusion methods. A large number 

 of determinations was made on a number of samples, two of 

 the latter being of known composition which were specially 

 prepared by one of the authors. 



The methods which have been compared may be divided 

 into two classes, viz. those for the determination of the total 

 sulphur and those for the determination of sulphur other than 

 that present in the insoluble sulphates. It was found that the 

 methods of the second class could not be relied upon to give ac- 

 curate results. 



The direct solution methods, those of Spence and Young, 

 and of Deussen, involve the use of concentrated nitric acid. This 

 was first suggested by Henriques but is objectionable because 

 it gives rise to low results. 



The direct fusion methods, those of Alexander, of the Joint 

 Rubber Insulation Committee, and of Kaye and Sharp, are 

 reliable only when the free sulphur content is low, and are there- 

 fore not applicable to routine analysis. 



The solution and fusion method of Frank and Marckwald 

 was found to be unreliable when the free sulphur was high. The 

 Waters and Tuttle method was found to give satisfactory re- 

 sults and is recommended for general use. 



A new suggestion is offered, namely, to determine separately 



' Detaile<l puixT to appear in the Bulletin of the Bureau of Standards. 



