LuckyWinner - 16-11-2020 at 09:50
a sodium iodide reaction was done.
potassium iodide was acidified with HCL
and then oxidized with H2O2 to get Iodine.
this iodine was washed with water.
iodine was then reacted with sodium thiosulfate
to make sodium iodide and Sodium tetrathionate in water.
2 Na2S2O3 + I2 → Na2S4O6 + 2 NaI
this water was then boiled down and flooded with ethanol
to precipitiate out the Sodium tetrathionate.
filtered it and simple distilled off the solvent.
yellowish sulfur impurities were present after this in the reaction and distillation flask.
it smells very bad, like rotten egg farts.
this was caused by the iodine not being washed properly
and still being acidic from the HCL which reacted with the sodium thiosulfate
to produce sulfur.
my suggestions
1) boil it down at over 200C , this is the evaporation point of sulfur to evaporate it all off.
2) boil it down and add water, sulfur is insoluble in it. then filter.
reddisolve Nai in water, filter again.
3) when distilling off ethanol of the NaI the yellow bad smelling sulfur does come over
into the distillate...
any non smelling alternative or better method?
any advice on this?
if this is done again , neutralize HCL with sodium carbonate to form NaCl?
Maurice VD 37 - 16-11-2020 at 13:09
The sulfur impurity is produced by some acid being mixed with thiosulfate, through the equation :
S2O3^(2-) + 2 H+ -> H2SO3 + S.
Iodine has not the odor of rotten eggs. The odor of rotten eggs is due to H2S, not to sulfur. Sulfur has no odor.