schaller: minasragrite 503 



ence, and the insoluble matter (mostly patronite) was air dried 

 and not heated before weighing. The results of the analysis 

 are given in table 1. 



The analysis, with the insoluble matter and associated melan- 

 terite, morenosite, and gypsum deducted and recalculated to 

 100 per cent, is shown with the ratios in table 2. 



The ratios yield the formula V 2 4 . 3S0 3 .16H 2 0, which is in- 

 terpreted as (V 2 2 )H 2 (S0 4 )3 • 15H 2 0, minasragrite being a highly 

 hydrated acid vanadyl sulphate. Quantitative determinations 

 (by permanganate titrations) show that all of the vanadium in 

 the mineral is in the tetravalent condition. 



Several hydrates of acid vanadyl sulphate are known. The 

 pentahydrate (V 2 2 ) H 2 (S0 4 )3.5H 2 is formed when the acid 

 solution is evaporated on a water bath at about 90°, and it can 

 be recrystallized from sulphuric acid at 100°. Lower hydrates 

 are formed at higher temperatures. 2 It is therefore to be ex- 

 pected that at ordinary temperature a higher hydrate than the 

 pentahydrate would form, and in minasragrite, formed at ordinary 

 temperature, 15 molecules of water represent the extent of the 

 hydration. 



It is interesting to note that Gerland 3 reported a hydrate 

 with 14 molecules of water, but later investigators have failed 

 to find it. Possibly Gerland's 14-hydrate was identical with 

 minasragrite. 



2 Koppel, J., and Behrendt, E. C. Verbindungen des vierwertigen Vanadins. 

 Zeitschr. anorg. Chem., 35: 154. 1903. Earlier references are cited by these 

 authors. See also Gain, Gustave. Sur quelques sulfates de vanadium tetravalent. 

 Comp. rend., 143:1154-1156. 1906. 



3 Gerland, B. W. Ueber einige Verbindungen des Vanadins. Ber. d. Chem. 

 Gesellsch., 9: 869. 1876. 



