XI, A, 6 



Witt: The Effect of Sulphide on Cement 



285 



washing were allowed to cool and were made up to definite 

 volumes. AUiquot portions, equivalent to 1 cubic centimeter of 

 the original sulphide solution, were removed and titrated with 

 ammoniacal zinc chloride solution. Some of the original sulphide 

 solution was titrated at the same time, so that the change in the 

 concentration of the sulphide in the two solutions could be 

 calculated. The results are shown in Table IX. 



Table IX. — Analysis of sulphide solution before and after contact with 



cement. 



Solution. 



Zinc solution 

 required per 

 cubic centi- 

 meter of sul- 

 phide solu- 

 tion. 



Sulphur as 

 sulphide per 

 cubic centi- 

 meter. 



Sulphur as 

 sulphide re- 

 moved by 

 cement. 





cc. 



Grains. 



Grams. 



Origrinal 



27.10 



0.0422 







25.37 



0.0396 



0.0026 





Although the green color caused by adding the sulphide solu- 

 tion to the cement appeared almost immediately, the above results 

 show that only 6.16 per cent of the sulphide was removed from 

 solution, either by oxidation or by the formation of an insoluble 

 compound. Considerable calcium and a trace of magnesium 

 went into solution. (Further test indicated that the presence of 

 the sulphide did not increase the solubility of the calcium hydrox- 

 ide.) The results were verified by mixing some cement of 

 known sulphate content with sulphide solution and allowing to 

 stand overnight. On analysis it was found that there was a 

 slight increase in sulphate. 



The preliminary experiments were carried out in contact with 

 the air, and it seemed likely that this might account for some of 

 the oxidation that took place. Moreover it was noticed that the 

 carbon dioxide in the air interfered by converting some of the 

 dissolved calcium hydroxide into carbonate. Consequently the 

 next experiments were made in an atmosphere of hydrogen. 



Five hundred cubic centimeters of water were placed into 

 each of two 750-cubic centimeter Erlenmeyer flasks. The flasks 

 were fitted with reflux condensers, and the water was boiled 

 from one to two hours to remove the air. The flame was then 

 removed, and a stream of hydrogen was passed through the 

 water until it had cooled to room temperature. Two 5-gram 

 portions of freshly ignited cement were then weighed and placed 

 in small glass capsules. One of the capsules was added to the 

 first flask while a stream of hydrogen was passing, so that no 



