164 W. 2L Bradley — New Silver- Tellurium Mineral. 



then picking out by the aid of a lens any fragments which 

 showed adhering white material. The method of analysis may 

 be briefly stated as follows : After dissolving the mineral in 

 nitric acid and filtering off traces of insoluble matter the silver 

 was precipitated and weighed as silver chloride. Tellurium 

 was essentially determined by precipitating it in the metallic 

 state by sulphurous acid. Traces of tellurium contained in 

 the filtrate were recovered by precipitating it as tellurium sul- 

 phide, the resulting precipitate being dissolved by a solution 

 of bromine in dilute hydrochloric acid and the tellurium 

 finally precipitated and weighed as Te0 2 according to the 

 method of Browning and Flint.* 

 The results of the analyses follow : 



I II Average Ratios 



Insoluble '38 "39 '39 



Ag 45-16 45-17 45-17 '418 l'OO 



Te ._ 54-62 54-89 54*75 -429) 



Fe -30 -15 -22 -003 Y 



100-46 100-60 100-53 



From the analysis it will be seen that the mineral gives a 

 ratio of practically Ag : Te : : 1 : 1, which fact points strongly to 

 the conclusion that the formula AgTe represents a new min- 

 eral species. The name empressite has been given to it by 

 Professor G-eorge on account of the fact that it was found in 

 this particular mine. While the above ratio does not give a 

 formula that is in harmony with the generally accepted views 

 relating to valence, nevertheless if considered from a metallo- 

 graphic standpoint it will be seen to be but one of many com- 

 pounds which show irregularities if attempts are made to 

 interpret them by means of valence. A table of such com- 

 pounds may be found in Desch's Metallography, f Some 

 typical examples are as follows : 



Silver- Aluminum Series. 



Ag 3 Al 

 Ag,Al 



Aluminum -Gold Series. 



Al 3 Au 



AlAu 



AlAu 3 



Al 2 Au 6 



* This Journal, xxviii, 112, 1909. 



f Longmans, Green & Co., London and New York; second edition. Appen- 

 dix, pp. 399-418. 



