346 Mr. D. Forbes on Evansite, a new Mineral Species, 



precipitate of the sulphides of lead and tin* fell, which was filtered 

 off, and the alumina determined as usual by precipitation by am- 

 monia. After ignition it weighed 5*90 grs., or equivalent to 38*36 

 per cent, in the mineral. 



The average of these two determinations of alumina will be 

 39-20 per cent. 



From the results of the above determinations the analyses will 

 now stand as follows : — 





a. 



b. 



c. 



Water . . . 



. 8-73 



6-45 



5-260 



Phosphoric acid 



. 4-09 



2-94 



2-630 



Alumina . . 



. 8-90 



5-90 



5-290t 



Insoluble (silica) 



. 031 



0-09f 



0-185 



Loss in analysis 



. 0-19 

 22-22 



1538 







13-365 



id calculating the percentages 



derived from these results,— 





a. 



b. 



c. Mean. 



Water .... 



39-29 



41-18 



39-37 39-95 



Phosphoric acid . 



18-42 



19-01 



19-73 19-05 



Alumina . . . 



40-05 



38-36 



41-51f 39-31 



Insoluble (silica) . 



1-39 



l-45f 



1-39 1-41 



Loss 



0-85 





0-28 



100-00 10000 100-00 100-00 

 From the above analysis the formula 3AP0 3 , P0 5 +18HO 

 may, I think, be safely deduced. This formula will, on calcula- 

 tion, represent the following percentage composition : — 

 3A1 2 3 = 153-78 = 39-75 Alumina. 

 6P0 5 = 71-00 = 18-36 Phosphoric acid. 

 18HO = 162-00 = 41-89 Water. 



386-78 10000 

 For comparison I annex a Table showing the chemical com- 

 position of all the hydrated phosphates hitherto announced as 

 having been found in the mineral kingdom. 



3Al203,2P05+12HO. 



2A1203,P05 

 + 5HO. 



2A1203.P05 

 + 6H0. 



2A1 2 03,P05 A1 2 03,P05 S 

 + 8HO. +8HO. 



Wavellite. Kapricite. 



Kalaite. 



Peganite. 



Fischerite. 



Gibbsite. " 



Barnstaple. Hungary. 



Silesia. 



Striegis. Niscbna Tugal 



. Mass. U.S. 



Phosphoric acid. 34*98 35'49 



30*90 



30*49 



29*03 



37-62 



Alumina . . . 37*18 39*59 



44*50 



44*49 



38*47 



26*66 



Oxide of iron 



1*80 



2-20 



1*20 



.... 



Oxide of copper 



3*/0 



.... 



0*80 



.... 



Gangue 



.... 



.... 



3*00 





Water . . . 28'00 24*92 



19*00 



22*82 



27*50 



35*72 



100*16 100*00 



99*90 



10000 



100-00 



100*00 



Fuchs. Stadeler. 



Zellner. 



Hermann. 



Hermann. 



Hermann. 



* Doubtless the lead had been in the tin as an impurity 



. 



t Determined as loss. 











