North and Conover — Mineral Sulphides. 641 



of beautiful hexagonal green crystals of ferric chloride. Reac- 

 tion undoubtedly follows the equation : 



6FeS 2 + 20SOC1, = 6FeCl 3 + 10SO, + 11S.C1,. 



Cinnabar. — The reagent appeared to be without effect on 

 cinnabar at the ordinary temperature, but reaction was com- 

 plete after a few hours heating at 150-175°. The solid product 

 formed consisted of a mass of white needle crystals which upon 

 analysis were found to be mercuric chloride. Reaction takes 

 place according to the equation : 



HgS + 2SOC1, = HgCl, + SO, + S,CI 2 . 



In addition to the above mentioned experiments in which 

 the product was analyzed quantitatively, the following tests 

 were made merely to ascertain whether decomposition of the 

 mineral results from heating with thionyl chloride. 



Pyrargyrite. — Decomposition took place slowly, but a very 

 appreciable change was noticed after 48 hours. After heating 

 for several days reaction appeared to be complete and the solid 

 matter in the tube was found to consist entirely of chlorides. 



Proustite. — Reaction proceeded much more slowly than with 

 pyrargyrite. After 48 hours only a slight change had taken 

 place, as was indicated by the appearance as well as by qualita- 

 tive tests. Thionyl chloride decomposes proustite with great 

 difficulty. 



Argentine. — The tube containing thionyl chloride and argen- 

 tite was heated for several days without the slightest change in 

 the appearance of the contents. Qualitative tests failed to 

 show even the slightest traces of silver chloride. The results 

 of this experiment are interesting inasmuch as the authors 

 have previously shown* that the artificially prepared silver 

 sulphide is decomposed readily by thionyl chloride giving 

 silver chloride. 



Covellite. — This mineral was completely decomposed by 

 thionyl chloride within 48 hours. 



Boulanger'de. — Boulangerite reacted readily with the re- 

 agent, the color of the powder becoming white within a few 

 hours. Qualitative tests showed the mineral to be completely 

 decomposed. 



Enargite. — Decomposition of enargite took place rapidly, as 

 was shown by the production of brown anhydrous cupric 

 chloride. 



Marcasite. — Specimens of marcasite from two widely sepa- 

 rated localities were employed. In both cases decomposition 

 took place completely within a few hours, each yielding the 

 green crystals of ferric chloride. 



* Loc. cit. 



