1871.] Dr. A. Schrauf on Mohjbdates and Vanadates of Lead. 455 



vanadium. Wulfenite, treated in the same way, gave a deep blue tint, 

 vanadinite a light yellowish- green, and chromate of lead a light yellowish 

 grey of the saline solution heated in contact with tin-foil. 



It would be desirable to ascertain experimentally the presence of other 

 metals besides lead, were not the scarcity of the material an obstacle to 

 any further experiments besides those of absolute necessity. 



Considering the whole of the experiments above described, the way 

 in which eosite is acted upon by heating in a glass tube, by hydrochloric 

 acid, alcohol, and bisulphate of potash, proves this mineral to be essen- 

 tially a vanado-molybdate of lead ; possibly with an excess of molybdenum, 

 as it may be supposed from the colorations caused by chemical action, the 

 presence of an undoubtedly minute quantity of chromium being concealed 

 by the chemical action of the prevalent constituents*. 



The investigations here detailed having ascertained the presence of lead, 

 molybdenum, and vanadic acid in eosite, it is still to be proved that the 

 chemical actions of vanadate and molybdate of lead are essentially different 

 from those manifested by eosite, and that consequently this mineral is to 

 be identified neither with the red varieties of wulfenite actually known, nor 

 with the crystals of dechenite, vanadinite, or descloizite. 



§ 3. Chemical Properties of the Chromo- Wulfenites. 



The late Professor H. Rose (Poggendorff's Ann. vol. xlvi. p. 639) is 

 known to have investigated the red varieties of wulfenite from Rezbanya 

 (Banat) and Siberia, and to have ascertained the presence of chromium in 

 them. I have before me cabinet specimens from Rezbanya, Ruskberg 

 (Banat), and Phenixville, which I shall comprehend here under the general 

 denomination of " chromo-wulfenites." The specimens from Rezbanya 

 being rather yellowish than pure red, I must confine my investigations to 

 those from Ruskberg and Phenixville. 



The matrix of the Ruskberg pyromorphite is cellular quartzf and 

 galena. A good number of rather bright, deep-red octahedral crystals of 

 wulfenite, 1-2 millims. in size, are fixed at the surface of the pyromorphite. 



The crystals of Phenixville are notably larger (2-4 millims.), and con- 

 creted into a crust on the surface of the matrix (quartz and pyromorphite). 

 Although apparently of even surface, these crystals show merely a peculiar 

 wax-like brightness. 



The red of eosite is deeper than that of crocoite ; it is somewhat more 

 intense than that of the Ruskberg chromo-wulfenite, and less mixed with 

 yellow than in the Phenixville specimens. The streak is browner in 



* The existence of vanadium, as accidentally entering into the composition of the 

 genuine wulfenites, was ascertained by Prof. Wohler on the occasion of his experiments 

 concerning the production of molybdic acid by the treatment of wulfenites (see Liebig 

 and Kopp, Ann. d. Chem. und Pharm. vol. cii. p. 383). 



t Euskberg lies in Austrian Banat, next to the threefold frontier between Banat, 

 Transylvania, and Wallachia. 



VOL. XIX. 2 N 



