Resistance and other Properties of Sulphur, 149 



Purification of the Sulphur. 



In the first method, for which I am indebted to Dr. Ruhemann, of 

 the Chemical Laboratory, Cambridge, bisulphide of carbon was 

 purified by being shaken with a little mercury and allowed to stand. 

 It was afterwards distilled over dry calcium chloride. These opera- 

 tions were repeated until the liquid was separated from other sul- 

 phides and from water. It was then saturated with sulphur and half 

 of the liquid distilled off. On cooling, crystals of sulphur formed. 

 These were removed and washed with fresh bisulphide to remove any 

 impurities that might have been left on their surfaces by the evapora- 

 tion of the adhering mother-liquid. They were then carefully broken 

 up and placed in a vacuum to remove as much, of the bisulphide as 

 possible before distilling. After remaining so for several days, they 

 were distilled in vacuo several times, the first portion coming over, 

 and that portion remaining behind being rejected in each case. 



The substance thus produced was of a beautiful light yellow colour, 

 and melted into a perfectly clear, transparent liquid, about the colour 

 of olive oil ; at higher temperatures it assumed the tint of port wine. 

 No traces of sulphuric acid, nor of chlorides, could be found, and the 

 absence of selenium was proved in the original substance, 



The only objection to this method of working is the presence of a 

 body whose solvent power for sulphur is so great, and the possibility 

 that the last traces are not removed even by repeated distillations in 

 vacuo. 



The second method consisted in distilling precipitated sulphur in 

 an atmosphere of chloride of sulphur, which removes hydrogen com- 

 pounds. After repeating this several times, it was distilled in vacuo. 

 As before, the middle portion only was retained. This method has 

 been found to give good results in the hands of some experimenters, 

 but I found very great difficulty in removing the chloride, being 

 obliged to reduce the body to a fine powder, and wash with water, 

 and finding this insufficient, finally distilled over a few small pieces 

 of pure zinc in vacuo, after which it was redistilled. 



This specimen was distilled altogether eleven times. 



The third method is the one used by Professor Threlfall, who takes 

 hyposulphite of soda, free from selenium, and dissolves it in distilled 

 water, then precipitates the sulphur by means of pure hydrochloric 

 acid. 



The reaction is shown by the well-known equation — 



Na 2 S 2 3 + 2HCl = 2NaCl + S0 2 + H 2 + S. 



All the substances produced, being either soluble in water, or gas 

 evolved during the reaction, except the sulphur itself, can be washed 

 out with pure water. 



l 2 



