OF ALUMINA. 313 



bath till it lost its liquid form, and became a 

 white dry crust. In this state it was nearly in- 

 soluble in water, though it was not quite desti- 

 tute of taste ; it did not deliquesce when exposed 

 to the air. 



20-25 grains of this salt being kept for half an 

 hour in a strong red heat, left 6*75 grains of 

 alumina, equivalent to 3 atoms of that earth. 



20-25 grains being digested with carbonate of 

 barytes, and the solution filtered and evaporated 

 to dryness, left 16-4025 grains of nitrate of ba- 

 rytes, which contains 6'7 grains of nitric acid. 

 This approaches so near 6*75 grains, that it is 

 evident the constituents of the salt are 



1 atom nitric acid 6'J5 

 3 atoms alumina 6-75 

 6 atoms water 6- 75 



20-25 



5. Phosphate of alumina. This salt was ob- phosphate, 

 tained by mixing together solutions of alum, and 

 phosphate of soda in the atomic proportions 

 no precipitate appears at first ; but if the mix- 

 ture be heated a white powder gradually falls, 

 which is phosphate of alumina. It is tasteless, 

 and insoluble in water ; but it reddens vegetable 

 blues powerfully. 9*125 grains of this powder, 

 well washed, and dried in the open air, being 

 heated to redness lost 3'375 grains. Hence, 

 the constituents are 



