id 182 
NaOH, Zn (OH), and their compounds if any, must be considered 
as those in a ternary system with the components: Na, 0—ZnO0—H, V0. 
The solubility-diagram of this system could now be completely 
determined at a constant temperature. As starting-material for these 
determinations we used NaOH, prepared from sodium; the ZnO being 
obtained in the following manner: Pure crystallized zine nitrate was 
precipitated with the required quantity of ammonia, thoroughly 
washed out with boiling water, the precipitate then being dried at 
140°—-150°. The oxide was also obtained by glowing precipitated 
zinc-carbonate, this oxide being less active, owing to the strong 
heating, it required a longer time to reach equilibrium. Both prepa- 
rations showed equal solubility. For the preparing of the hydroxide, 
vide infra. The water had been distilled and boiled out before use. 
All the determinations were executed in a thermostat of 30,0° C. 
In table 1 and the accompanying diagram 1 a survey of the results 
is given. All the number-values represent weight percentages of the 
saturated solution. As it proved extremely difficult to accurately 
isolate the solid phases, we determined the composition in yee 
all cases according to SCHREINEMAKERS’s rest-method. 
In determining the curve AB we added ZnO as solid phase *); the 
solubility of this substance appears rapidly to increase with growing 
NaOH-concentration. As appears from the second curve BC of the 
isotherm, the sodium-zincate of the formula: Na,OZnO04H,0 preci- 
pitates from the solution, while constantly the NaOQH-concentration 
is increasing. The curve CD, where solutions are saturared by the 
monohydrate of sodium-hydroxide: NaOH. H,O |Na,O .3H,O] 
immediately joined to BC. According to the melting-diagram NaOH—H,O 
determined by PickerinG*) this hydrate is the only stable compound 
of NaOH with water at 30°. 
Consequently only one stable zincate arises at 30°, having the 
formula: Na,O.2nO.4 H,O. All the other zincates described in the 
literature, must be considered either as metastable or as not existing at all. 
The opinion of Hanrzscu*) concerning the colloidal nature of the 
solutions, does not hold true either, as will appear still more 
decidedly later on. | 
Properties, preparation, etc. of the sodium-zincate 
Na,O.Zn0 .4H,O. 
The diagram referred to already shows that the sodium-zincate 
1) Except in the numbers 26 and 29 (vide infra). 
3) Journ. Chem. Soc. 63, 890 (1893). 
3) Loc. cit. 
