Genth and Vom Rath.l du4 [April 17, 



account of the geological position and the accompanying minerals which 

 he had observed. 



A few months ago a highly interesting find was made at the Sierra 

 Grande, which furnished some beautiful specimens of very rare species, of 

 which we received a sufficient supply for investigation from Mr. N. H. 

 Muhlenberg, in Lake Valley, and his representative in Reading, Pa., Mr. 

 Theodore A. Kendall, to whom we are greatly indebted for their liberality, 

 also to Mr. Robt. C. Canby, at Pueblo, Col., who has kindly furnished the 

 writer with the vanadinite from the Sierra Belja. 



In the following investigation the crystallographic measurements and 

 figures are by Gerhard vom Rath, and the analyses, &c., by F. A Genth. 



It may be well to give a general outline of the methods employed for 

 the analyses of the vanadates, described in this paper. 



After dissolving in very dilute nitric acid, the insoluble residue was 

 filtered off, then treated again two or three times with dilute nitric acid in 

 order to bring all the vanadates into solution. This was especially neces- 

 sary in the case of the dark descloizites, but, notwithstanding this, some 

 of the constituents of this mineral remained undissolved, and appreciable 

 quantities of lead, copper and zinc were retained, probably by the man- 

 ganese dioxide which was present in considerable quantities. These bases 

 were determined and their quantity added to the main portion. 



In the filtrate the chlorine was precipitated by a few drops of silver 

 nitrate, the excess of silver removed by just enough hydrogen chloride 

 and the filtrate from the silver chloride evaporated nearly to dryness. A 

 large excess of strong hydrogen sulphide water was then added and the 

 beaker put at a warm place for two days. Lead, copper and arsenic were 

 precipitated as sulphides, but also, invariably more or less zinc,* although 

 the solution was still strongly acid. After two days' standing, the solution 

 had yet a strong odor of hydrogen sulphide. It was filtered off, and the 

 arsenious sulphide separated from the sulphides of lead, copper and zinc, 

 by digestion with sodium hydrate, the filtrate precipitated with hydrogen 

 chloride ; the arsenious sulphide, thus obtained, oxydized with strong 

 nitric acid into arsenic acid, which was weighed as pyro arseniate of mag- 

 nesium. The precipitate containing lead, copper and part of the zinc as 

 sulphides, was oxydized with strong nitric acid, sulphuric acid was then 

 added and evaporated until the nitric acid was completely expelled. In 

 the filtrate from the lead sulphate the copper was precipitated as sulphide 

 and weighed as oxide, and the zinc converted into sulphide, after neutrali- 

 zation with ammonia, and added to the main portion. 



The filtrate from the first hydrogen sulphide precipitate was evaporated 

 and the tetraoxide of vanadium re-converted into vanadic acid by the nitric 

 acid present, whereupon, the solution was boiled with sodium carbonate 

 to separate the zinc, manganese and iron from the greater part of the 



*In the analysis of descloizite, a2, the zinc was lost, because the filtrate from 

 the lead sulphate which contained a portion of it, M'as accidentally thrown 

 away. 



