140 
values that fall on curve III with satisfactory accuracy; the bar- 
shaped crystals of y too proved to be present in the state of equi- 
librium. Consequently § has been hydrated and converted into y. 
In pure water this hydration takes place only very slowly; in the 
lye-solutions however much more quickly. The cause of this is 
probably that in the latter solutions the Al,O, dissolves primarily 
and the hydroxide separates from this solution. 
The determinations with the products © and « are about situated 
on the curves I and II; this too shows that the hydration takes 
place very rapidly in proportion to the stabilisation to product y. 
Besides it shows that the differences between the product a, @ and 
y have not disappeared after the heating, in other words that also 
Al,O, exists in various forms. All however are metastable at 30° 
as regards the trihydrate. 
CUO, 
ALO; 34,0 
Y¥%ay0. 302,03. 16H,0. 
2,03. 10,0 
10 Tie a0 
