Re/gar chei on Alumine* 3j 



By a microfcope of a magnifying power equal to ooo or 

 3-0," it appeared, as Schreber has remarked, that it is com- 

 pofed of imall tranfparent prifmatic cryftals, comprefTed and 

 terminated by blunted pyramids. I was not able to difcover 

 this cry utilization in alumine prepared artificiiiliy. 



At the firft degrees of incandefcenee it lbfes about two- 

 thirds of its weight. Alumine lofes only fifty-eight hundredths. 



A decoction of it in water did not change teft paper, but 

 it became turbid by the oxalate of potafh and folution of ba- 

 rytes. This folution, evaporated to drynefs in a gentle heat, 

 left a refiduum which was only the 0*022 part of the alumine 

 employed. It was compofed of fulphate of lime, and a yellow 

 matter, fufceptible. of being carbonated by combination, and 

 iimilar to vegetable extract. 



A gramme (15*44 grains) of the argil of Hales, difiolved 

 cold, a hundredth part excepted, in nitric acid, without pro- 

 ducing any effervefcence. None was produced when the folu- 

 tion was made at a heat equal to 6o° of Reaumur (167 Fahr.). 

 The fulphuric acid diflblved it alio cold, almoft entirely, and 

 without effervefcence. 



A folution of this earth by the nitric acid was not rendered 

 turbid bv muriate of platina. 



The lame folution was precipitated, cold, by carbonate of 

 ammonia in excefs. The liquor, when filtered, was expofed 

 to ebullition, to try whether it contained glucina. By this 

 operation it became pretty turbid ; the new fubftance was 

 carefully collected, and weighed, when dried at the tempe- 

 rature of the atmofphere, about fetfen -hundredths of the na- 

 tive argil : but I doubt whether it was glucina^ for it pro- 

 duced no effervefcence when diflolving in nitric acid, as glu- 

 cina would have done in the like cafe, according to the expe- 

 riments of Vauquelin. A folution of it in nitric acid in ex- 

 cefs was not precipitated by pruffiate of potafh, oxalate of pot- 

 afli, and fulphuric acid ; but it was by ammonia. This pre- 

 cipitate was foluble in potafh; it was therefore not gadolinite. 

 Was it a new fubftance, or alumine united to a bale, which 

 gave it the property of diflolving in carbonate of ammonia? 

 Thofe who poffefs argil of Hales in fudicient quantity may be 

 able to determine this queftion. 



Potafh was able to diilblve, an imponderable quantity of 

 the oxide of iron excepted, the alumine precipitated from the 

 nitric acid by the carbonate of ammonia in the preceding ope- 

 ration. This alumine, feparated from potafh, cryftallized in 

 oetaedra with the alkaline addition requifite in fuch a cafe. 



The argil of Hales, projected into nitre in fufion, produced 

 no detonation ; it mowed only in oblcurity a very faint blue 



C 2 trace, 



