278 P>'°f- Fiichs on Lasionite and Wavellite. [Oct. 



Therefore 100 parts contain : 



Alumina 36*56 



Phosphoric acid 34-72 



Water 28-00 



99-28 



Examination of Wavellite.*' 



Wavellite, to which the names of devonite and hydrargillite 

 have been also given, in its physical properties does not differ 

 from lasionite. Before the blow-pipe it exhibits the same 

 characters, loses the same weight in the fire, and is acted on in 

 the same way by the acids and alkalies. 



The first analysis which I made of it was performed in the same 

 way as the preceding, but the result was very different, as I 

 obtained 54-32 per cent, of alumina, and 25-68 per cent, of 

 phosphoric acid. When to these we add 28 per cent, of water, 

 there is an excess of 8 per cent. ; but it was not difficult to 

 explain whence this difference and this excess proceeded. I had 

 employed a greater quantity of potash in this analysis than in the 

 preceding, and I boiled it for an hour over the precipitated 

 phosphate of lime. This occasioned the solution of some phos- 

 phate of lime in the potash liquid which contained the alumina ; 

 and this portion was mixed with the alumina when that earth 

 was thrown down by sal-ammoniac. When now the eight parts 

 of excess are considered as lime, and the phosphoric acid com- 

 bined with it, and dissolved in the potash ley along with it, is 

 considered as forming not neutral, but, as is probable, biphos- 

 phate of lime, which, according to my experiments, contains 

 53*4 per cent of phosphoric acid, and of course must be 

 composed of 8 lime + 9*16 acid = 17-16 parts. This, being 

 subtracted from the alumina, and 9*16 parts being added to the 

 phosphoric acid, we obtain the constituents of wavellite as 

 follows : 



Alumina 37-16 



Phosphoric acid 34-84 



W r ater 28-00 



100-00 



As doubts might be entertained respecting the accuracy of 

 these numbers, I considered it as necessary to repeat the 

 analysis ; and to avoid the uncertainty produced by the solution 

 of the phosphate of lime in the potash ley, I proceeded in quite 

 a different way.f I employed for the decomposition a solution 



* The specimen of wavellite which I employed in this analysis was from Barn- 

 staple. ] was indebted for it to Major Petersen. 



+ Theodore de Sausrure, as far as I know, was the first person who observed that 

 phosphate of lime is soluble in potash. — (See Gehlen's Journal fi\r die Chemie und. 

 Physik, ii. 668 — 702.) Klaproth likewise, in his experiments on the phosphoresc- 



