Similar to that of Donium. 21 



did to several friends in private, in April last — but before 

 making it known, I was desirous of completing the exami- 

 nation of the other ingredients of the mineral, — which, 

 however, I have not as yet been able to accomplish to my 

 satisfaction. 



The substance under examination contains a considerable 

 portion of alumina, or rather of a substance which is so- 

 luble in potassa and re-precipitated by muriate of ammonia, 

 yielding crystals of alum with sulphuric acid and potassa. 

 My attention was first called to the new substance, by ob- 

 serving that this alumina was unusually soluble in liquid 

 ammonia; next the pale drab colour of the precipitated 

 alumina, and its change from white to brown by exposure, 

 seemed to indicate the presence of iron or manganese, 

 which, however, I could not detect : and lastly, the fluctu- 

 ating quantities of alumina obtained, led me to examine 

 not only the liquid in which the alumina had been sepa- 

 rated from potassa by muriate of ammonia, but also that 

 in which the sulphate of alumina had been decomposed by 

 excess of carbonate of ammonia, in both of which, there 

 was a substance, which, dissolved in nitric acid and thrown 

 down by ammonia, gave a precipitate rapidly changing from 

 white to pale brown. I then suspected something extraor- 

 dinary, and the addition of hydro-sulphuret of ammonia 

 settled the question, by giving a dense green precipitate. 

 Then recollecting how beautifully the crystals of alum were 

 truncated in ther angles and edges. I applied the same test, 

 after having decomposed and re-dissolved in potassa, and 

 with a similar result. Mr. Richardson does not allude to 

 the fact, but my sulphuret soon changes from green to a 

 yellowish white on exposure in a moist state, on the filter ; 

 and the alkaline solution has a bright green colour from 

 holding some of the sulphuret in solution, which also slowly 

 undergoes the same change with deposition of whitish 

 flocculi. The gr^^n precipitate readily dissolves in nitric 

 acid, with evolution of fumes of sulphuretted hydrogen : 

 and when concentrated by a gentle heat, it has a yellowish 

 colour. 



With this solution, potassa and ammonia give white pre- 

 cipitates changing to yellow, the carbonates of the same 



