234magnum - 20-2-2014 at 01:00
I want to make sodium zincate solution from ZnO by mixing 1 gram ZnO and 4 gram NaOH.
Nothing happened. ZnO still there, sink in the bottom.
Then I heat it until boiling, and ZnO still there.
I buy ZnO and NaOH from chemical store.
Do I make some mistake? Please help...
Oscilllator - 20-2-2014 at 02:54
Try either boiling it for longer, or dissolving it in an acid like HCl first. Then add the sodium hydroxide to the soluble zinc salt.
If the zinc oxide does not dissolve in the acid, then it is most likely calcined. If this is the case then you are basically buggered, since it
requires very harsh conditions like molten sodium hydroxide to dissolve calcined material.
blogfast25 - 20-2-2014 at 06:05
My own ZnO is incredibly inert. Fusion with molten NaOH or KOH will crack it though.
You just need a decent steel or nickel crucible for that. After cooling, dissolve the crucible's content in sufficient water and filter off insoluble
residue.
[Edited on 20-2-2014 by blogfast25]
234magnum - 21-2-2014 at 00:50
Thank you, it worked 
Dissolving in acid is much faster than boiling it.
Thanks again.
sasan - 23-2-2014 at 08:38
dissolve it in the acid.add sodium hydroxide,do not use excess(because zinc hydroxide dissolve in sodium hydroxide and make zincate,the problem is
NaCl existing in solutions)separate zinc hydroxide from the solution,then move it to another glassware and add water,then add sodium hydroxide in
small portions till the zinc hydroxide completely dissolves
by adding sodium hydroxide for each small portions,wait for minutes,because it takes time to form zincate ion
at the end there will be undissolved sodium zincate at the bottom of glassware because of the solubility of the product
I was doing it some times ago.it must be work
sasan - 24-2-2014 at 08:31
by the way boil the solution while adding NaOH in small portions