Chukch — On Native Phosphates of Aluminium. 561 



system deduced from the study of other members of this series, "we 

 may arrange its formula thus — 



3A1A, P2O5, 8H0O + lOaq. 



Here the 10 aq. represent those molecules of water which are disen- 

 gaged in the water-oven. How the 8 H2O are combined with the 

 AI2O3 and the P2O5 has not been ascertained, but this may be said, 

 that the fixity of this water at or near 100° forbids the assumption 

 that in evansite we have an association of AI2P2O82 aq. with 2 A12H606- 

 If there be no doubt that the entire molecule of evansite contains 

 not less than 1 8 of HgO, the relation of liskeardite^^ to this species will 

 have to be reconsidered. If that mineral be "an arsenical evansite " 

 it should contain 2 molecules of water more than have been assigned 

 to it. Its formula has been expressed hitherto thus — 



3E2O3, AS2O5+ I6H2O, 



where 1^203 represents alumina with some ferric oxide. 



§ XY. The following Table will prove useful in comparing the ex- 

 perimental numbers given in this Eeport with those required by theory. 



Proposed Classefication' of ALTTMiNniM Phosphates. 



Species. 



Formula- 



Theoretical Percentages of 



ALO3 



(102-6). 



P0O5 



(l"42). 



H„0 



(18) 



group I. 



P 



AI2O3, P2O5, 2 aq. 



36-56 



50-61 



12-83 



Vabiscite, . . . 



AI2O3, PoOg, 4 aq. 



32-40 



44-85 



22-74 



Zepharovichite, . 



AI3O3, P2O5, 6 aq. 



29-09 



40-27 



30-63 



p 



AI2O3, P2O5, 8 aq. 



26-40 



36-54 



37-05 



GROUP II. 



COERULEOLACTITE, . 



3AI2O3, 2P2O5, 10 aq. 



39-83 



36-79 



23-32 



PWavellite, . . . 



3Al203,2P205,llaq. 



38-97 



35-95 



25-07 



PStriegisane, . . 



3Al203,2P205,12aq. 



38-10 



35-16 



26-74 



13 N. S. Maskelyne, Nature, August 16th, 1878. 



