teodor - 30-9-2019 at 23:18
I want to prepare Na2[Sn(OH)6]. I want to compare its properties (chemical properties, crystals shapes with different cations) with K[Sb(OH)6] which I
already prepared. I am searching for advice.
I found the procedure in Brauer:
"A solution of SnCl4 in very dilute hydrochloric acid is neu-
tralized to methyl orange with carbonate-free NaOH. The SnO 2 •
aq. precipitate is filtered off, washed until chloride-free with
H2O, and added in portions to an excess of concentrated, 100°C
NaOH, in which it dissolves rapidly, affording a clear solution.
The crystalline hexahydroxostannate precipitates after a short
time. The crystal slurry is filtered in the absence of CO2 and
washed with 30% NaOH and then several times with ethanol and ether."
First, I think I can substitute SnCl4 with a mixture of SnCl4 + SnBr4 which I can get by oxidation of SnCl2 by bromine water (according to Treadwell).
The method with bromine allows to closely reach the point when all SnCl2 is oxidised (by colour change). Because I need it in solution I think this
method is the best.
I am not quite sure about proper and affordable method of "filtering the crystal slurry in the absence of CO2". Can you recommend me something?
teodor - 1-10-2019 at 22:49
For preparing the bromine water I plan to react hydrobromic acid with chlorine. HBr/HCl contamination should not interfere with the experiment
results.
teodor - 12-10-2019 at 09:47
So, I prepared bromine water and did oxidation of Tin(II) to Tin(IV) until slightly yellow color of solution. This was a spectacular process and we
made a short video - https://youtu.be/CqhkAXntZS4 .
Before going to the next stage (getting SnO2 aq) I should prepare CO2 free alkali solution. I think to use Ba(OH)2 to remove CO2. (May be substitute
NaOH with Ba(OH)2 in the preparation procedure?)
woelen - 14-10-2019 at 03:12
Boiling the water, before dissolving your alkali also helps removing CO2.
The alkali, used in this experiment, also must be fresh and of decent quality. Otherwise it will contain carbonate and then the meticulous removal of
CO2 from the water is a moot point.