Chemistry. — “The zincates of sodium. Equilibriums in the system 
Na,O-£nO-H,O”. By Dr. F. Goupriaan. (Communicated by 
Prof. J. BÖRSEKEN). 
(Communicated in the meeting of June 28, 1919). 
The data we find in the literature about the influence of the 
strong bases of light metals on the insoluble weak hydroxides of 
heavy metals, are extremely contradictory and ill-defined. So it is 
generally assumed that the hydroxides of zinc, aluminium, lead and 
tin display an amphoteric character, so that in an excess of strong 
base they ‘dissolve’ under the formation of salts. It is supposed on 
tbe other hand that the hydroxides of numerous other heavy metals 
do not show any propensity to form similar salts and by this the 
stronger electro-positive character of these metals is thought to 
reveal itself. And yet it is a fact that the hydroxides of the so- 
called strong electro-positive metals can likewise in some circum- 
stances display an amphoteric character; nay even cuprum hydroxide 
can dissolve in a concentrated solution of NaOH or KOH. Hence 
the differences occurring with the metalhydroxides are probably only 
of a quantitative nature and it will be worth while to investigate 
to what extent the different hydroxides show this phenomenon and 
what compounds arise in this process. This is in the first place of 
importance for analytic chemistry, where numerous separations are 
due to the difference in solubility of the hydroxides; next investi- 
gations about this subject can give us a more definite insight into 
the mutual affinity of the metaloxides and metal-hydroxides. 
Up till now it has not yet been ascertained what compounds are 
formed under the influence of hydroxides on strong bases and under 
what circumstances they are stable. In a pure state they are not 
isolated and accurately delineated. We are still quite in the dark 
about the nature of the hydroxides themselves. For as a rule we 
obtain these substances as voluminous, gelatinous products, and the 
question arises whether we are to consider these as solid phases of 
a constant or variable composition or as liquid ones of a great 
viscosity. The great difficulties which the procuring of these substances 
in a pure state, involves, are probably the cause of the very few 
exact data we have about the subject under discussion. 
