318 Intelligence and Miscellaneous Articles. 



100 of sulphuret of zinc decompose 3 of chloride of silver 



100 .... cadmium ..14- .... 



100 .... bismuth .. 2 .... 



100 lead . . 5 .... 



1 00 protosidphuret of tin "a • • • • 



100 of bisulphuret of tin ..SO .... 



100 protosulphuret of copper 360 .... 



100 arseniuret of antimony 120 .... 



100 .... cobalt 166 .... 



In operating with natural sulphurets, the authors remarked very 

 considerable differences in their decomposing power. They attri- 

 bute these differences to the presence of small quantities of sulphu- 

 rets or arseniurets of very high decomposing power ; and they sup- 

 pose they may sometimes attach to the molecular condition of the 

 bodies. They found, for example, that a very pure and well-cry- 

 stallized blende from Kiinigsberg possessed decomposing power 

 equal to that of artificial sulphuret of zinc; while a blende equally 

 pure and as well crystallized, but coming from Radna, had a decom- 

 posing power which was twice as weak, and yet these two blendes 

 were of equal density. 



The authors draw the following conclusions from the results of 

 their experiments : — 



AH pure metallic sulphurets possess the power of decomposing, 

 under certain circumstances, a given quantity of chloride of silver, 

 and even of other insoluble chlorides. This power appears to be 

 modified in some cases by the molecular condition. 



The decomposition of chloride of silver by sulphurets may be 

 effected, — 1st, by double decomposition ; 2nd, by reduction; 3rd, 

 by simultaneous reduction and double decomposition. 



Natural sulphurets sometimes exhibit very high absorbent powers, 

 on account of the presence of minute quantities of foreign sulphurets 

 or arseniurets, acting by the reduction of the chloride of silver. 



The decomposing action of sulphurets is exerted proportionally on 

 the bromide of silver, and it is but slightly appreciable on the iodide. 



In these phaenomena the solvent exerts no influence ; for the 

 same results are obtained, except as to time, by simple contact aided 

 by water. 



The general fact of the decomposition of insoluble chlorides by 

 sulphurets appears then to render it probable that, in natural sul- 

 phurets, the silver is in the state neither of chloride nor bromide. 



Having then shown the improbability of the presence of metallic 

 silver or chloride in the natural argentiferous sulphurets, the authors 

 are of opinion that it must exist in the state of sulphuret ; but if 

 this conclusion were correct, how does it happen that blende, pyrites 

 and galena, do not yield silver to mercury? Is not the sulphuret 

 of silver almost as readily acted upon by mercury as metallic silver 

 itself? The authors propose shortly to communicate the second part 

 of this inquiry to the Academy. — Comptes Rendus, Juillet 26, 1 847. 



