158 D-rushel and Elston— Sulphide Sulphur. 



phate condition by chlorine water or bromine water and 

 weighed as barium sulphate. Tins method was used as a con- 

 trol to check up the results obtained by the colorimetric method. 

 In this method the hydrogen sulphide was liberated and 

 absorbed as suggested by Fresenius and aliquot portions of the 

 sulphide containing potassium hydroxide solution were trans- 

 ferred to the distillation flask and the previously described 

 procedure was followed. A comparison of the results obtained 

 by the two methods on several samples of coke is found in 

 Table II. 



Table II. 



Coke Analysis. 



Sulphide sulphur found 

 by Fresenius grav- by colorimetric 



imetric method method 



0-049$ 



0-050$ 



0-050 



050 



0026 



0-025 



0-025 



0026 



0-027 



0-025 



(3) In paper analysis. Another practical application of this 

 method of determining sulphide sulphur is in paper analysis. 

 In order that tissue paper may be used for wrapping polished 

 metal without producing a tarnish the paper must be relatively 

 free from sulphide sulphur. A weighed amount of paper, 

 1 gram to 2 grains, is cut into small pieces and transferred to 

 the distilling flask and digested with gently boiling 05 per 

 cent hydrochloric acid, collecting the hydrogen sulphide as 

 lead sulphide on lead acetate paper as previously described. 

 A number of samples of tissue paper were examined and in 

 those samples which contained sulphide sulphur the amounts 

 varied from - 0002 per cent to 0-001 per cent. Papers which 

 contained the larger amounts of sulphide sulphur when used 

 for wrapping polished silver pieces usually produced a marked 

 tarnish in the course of two or three weeks. 



This colorimetric method of estimating very small quantities 

 of sulphide sulphur is very rapid, fairly accurate, and has a 

 number of practical applications. 



