640 North and Conover — Mineral Sulphides. 



Art. XLIV. — Decomposition of Mineral Sulphides and Sul- 

 pho-Salts by Thionyl Chloride • by H. B. Nokth and C. B. 



CoNOVER. 



In another journal* the authors have recently described an 

 investigation of the action of thionyl chloride on sulphides, the 

 study being limited entirely to compounds prepared in the 

 laboratory by precipitation or by fusion. Reaction was found 

 to proceed according to the following general equation in which 

 M represents a divalent element : 



MS + 2SOC1, = MCI, + SO, + S,C1 



■2' 



Deviation from this was found only in two or three cases in 

 which oxidation as well as chlorination took place. 



Inasmuch as minerals are frequently less readily attacked by 

 reagents than are artificially prepared compounds, the study 

 has been continued to the reaction of thionyl chloride on a 

 number of mineral sulphides and sulpho-salts. 



The minerals used were carefully selected specimens. The 

 fragments chosen were powdered in an agate mortar, the pow- 

 der dried at 110° and preserved in tightly stoppered tubes. 

 The reactions were carried out in sealed glass tubes, about a 

 gram of the powdered mineral and an excess of thionyl chloride 

 being heated together in each experiment. The temperature 

 employed was 150-175° C. 



When reaction appeared to be complete, the tubes were 

 opened, the solid contents well washed with carbon disulphide, 

 dried and analyzed. Sulphur dioxide and sulphur monochlo- 

 ride were found to be present in every experiment in which 

 reaction took place. In nearly all cases a small amount of 

 white insoluble matter remained when the sample taken for 

 analysis was dissolved. This proved to be silica. In the three 

 quantitative experiments this silica was weighed and the weight 

 deducted from that of the sample taken. 



Galena. — Thionyl chloride did not react with galena when 

 the two were brought together at the ordinary temperature. 

 When heated at 150° the solid contents of the tube gradually 

 whitened. Reaction appeared to be complete after 40 hours. 

 Analysis of the white solid proved it to consist almost entirely 

 of lead chloride with a trace of ferric chloride. Reaction takes 

 place as follows : 



PbS + 2S0C1 2 = PbCl, + SO, + S 2 CI,. 



Pyrites. — Pyrites and thionyl chloride did not react in the 

 cold, but at 150° reaction took place readily with the formation 



* Journal of the American Chemical Society, Nov. 1915. 



