L56 Drushel and Elston — Sulphide Sulphur. 



this tube a filter paper moistened with a dilute solution of 



lead acetate was smoothly fitted and tied, so that the steam 

 passing up through the tube and carrying hydrogen sulphide 

 was required to pass out through the lead acetate paper. A 

 similar tuhe with the internal diameter of its larger end about 

 :i);""" was also prepared and used for sulphide sulphur samples 

 containing O'OOJ per cent or more of sulphur. 



A. solution of sodium sulphide was made up with pure dis- 

 tilled water and carefully standardized. The solution was then 

 diluted to contain exactly 0*01 per cent of sulphide sulphur. 

 This solution was used for making up standard solutions con- 

 taining 0-0002, 0-0004, 0-0006, 0-0008, 0-001, 0-002, 0-003 and 

 O'004 per cent of sulphide sulphur respectively, taking care to 

 use distilled water free from traces of nitrites in making the 

 dilutions. It was found that the more dilute sulphide solu- 

 tions when made up with ordinary distilled water lost their 

 sulphide content either wholly or in part on standing for 

 several hours in stoppered bottles. This difficulty was obviated 

 by using nitrite free distilled water in making up the solutions. 



Carefully measured portions of l cm3 to 5 cm3 of the standard 

 solutions were pipetted into the 100 cm3 flask and 25 cmS of hydro- 

 chloric acid of about - 5 per cent strength were added. The 

 flask was immediately attached to the condenser tube fitted 

 with moistened lead acetate paper as previously described. The 

 mixture was then gently boiled for a few minutes at such a 

 rate that the steam issued not too rapidly from the upper 

 end of the condenser tube. In this way the sulphide sulphur 

 was quantitatively liberated as hydrogen sulphide and evenly 

 deposited as lead sulphide on the moistened lead acetate paper. 

 The undecom posed lead acetate was then washed out, the 

 paper dried and labeled with the amount of sulphide sulphur 

 present as one of the set of standard stains. In the same 

 way complete sets in duplicate were prepared ranging in sul- 

 phide sulphur from 0-0002 per cent to 0'004 per cent. 



In order to determine the accuracy with which sulphide sul- 

 phur may be estimated in this way one of us made up a series 

 of sodium sulphide solutions which the other estimated by the 

 method outlined. The results are given in Table I. The 

 first column shows the amount of sulphide sulphur in the solu- 

 tions as made up. In the second column are the estimated 

 amounts of sulphide sulphur. 



In making these estimations the larger condenser tube was 

 used where a preliminary trial indicated that the amount of 

 sulphide sulphur was equal to or greater than - 001 per cent. 

 In all other cases the smaller tube was used. The maximum 

 error, depending upon the amount of sulphur present, with the 

 larger tube was 0-001 per cent and with the smaller tube - 0003 



