Chemistry. — “The aluminates of sodium. Kquilibriums in the 
system Na,O—Al,O,—H,0O”. By Dr. F. Gouprraan. (Communi- 
cated by Prof. J. BöESEKEN). 
(Communicated at the meeting of April 23, 1920). 
Introduction. 
In a preceding paper’) a survey was given of the equilibriums 
that may arise at 30° in the system: Na,O—ZnO—H,O. Among 
other things the range of existence of the zincate of sodium and the 
stability-relation between ZnO and zinchydroxide were determined 
in this paper. In view of our still very slight and incomplete know- 
ledge concerning the corresponding compounds of other metals, it 
was now tried also to determine similar equilibriums of some of 
these metals. The following will give a brief survey of the results 
obtained in the system: Na,0—Al,0,—H,0. 
Although the existence of aluminates has long been suspected and 
in nature some even seem to occur in a crystallized state in some 
minerals (e.g. the spinels), not a single exact datum regarding these 
bodies is to be found in the literature. To be sure it is known that 
also in elaborating the mineral bauxite by treating it with soda, 
aluminium is fixed as an aluminate, but we are by no means 
acquainted either with the composition or with the stability of these 
compounds. It is true that several investigations have been made in 
this direction, but in none of these the solid phases have been 
isolated. The compositions that are therefore given to the aluminates 
have been determined in a more or less indirect way and serious 
objections may always be raised to the methods applied in doing so. 
Therefore it is not wonderful that the results are often in serious 
mutual contradiction. A short summary of the knowledge obtained 
up till now about the aluminates, from which this will further 
appear, is the following: 
Cavazzi*) first suspected the existence of these compounds and 
ascribed to them formulae like: NaAlO, on the ground of his obser- 
vation that 1 gram-atom Al will dissolve in 1 gram-molecule NaOH. 
1) Proceedings XXII, 179 (1919). 
*) Gazz. chim. ital. 15, 205 (1885). 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
