185- 
mixture will be obtained containing a greater or smaller quantity 
of zincate-crystals. The formulae for such products are devoid of 
sense and should consequently disappear from the literature. 
Stability, preparation, etc. of zine hydrowide. 
It is generally known, that as a rule zine hydroxide is obtained 
as a gelatinous, voluminous mass. Now it was essential for the 
present investigation to determine whether this phase has a constant 
or a variable composition and to find out its stability regarding 
ZnO. There are many indications to be found in the literature that 
the hydroxides obtained in varying ways do not possess the same 
composition. HULER') prepared from the nitrate hydroxides which 
proved to havea varying solubility in ammonia. Herz *) and Hanrzscu *) 
point out the great difficulties involved in obtaining Zn(OH, in a 
pure state and specially the tenacity with which it retains sulphate- 
ions. It seems, that it is easier to obtain a pure hydroxide from 
the chloride or nitrate than from the sulphate. With the experiments 
made to confirm this statement, | proceeded from pure ZnO, which 
was dissolved in hydrochloric acid and nitric acid, upon which the 
hydroxide was precipitated by means of the addition of the quan- 
tity of ammonia calculated. If this precipitate is washed out with 
boiling water it almost immediately becomes more gritty, heavier 
and less gelatinous. After washing out a few times and following 
it up by desiccation at 100°, the product appeared to contain only 
0,6 °/, water. In conseqence of the washing-out the hydroxide is 
converted into oxide already at 100°. Hence Zn(VH), at 100° is no 
longer stable. 
We then tried to achieve a pure hydroxide by washing out at 
room-temperature. It appeared however, that even after prolonged 
and continued extraction the products were still chloridie or nitritic. 
During the first hours of the extraction we observe a considerable 
decrease in the concentration of the adsorbed ion, afterwards it falls 
but very slowly. The following figures will further illustrate this 
statement: 
Hence it is practically impossible in this way to obtain a pure 
hydroxide from the chloride. The products from sulphate and nitrate 
yielded similar results and though it is stated in the literature, that 
the nitrate-ion is much less strongly absorbed than the other ions, 
we determined that even after an extraction continued for days the 
) Ber. d. deutsch. Chem. Ges. 36, 3400 (1903). 
§) Zeitschr. f. anorg. Chem. 30, 280 (1902); 31, 357 (1902). 
3) Loc. cit. 
