rocketman
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Potassium Selenite
Info on Potassium selenite is scarce.
Preparation of potassium selenite---White crystals if done right.
Often confused with Selenate and selenide.
Selenium: Geobotany, Biochemistry, Toxicity, and Nutrition
By Irene Rosenfeld, Orville A. Beath
"Prepared by dissolving SEO2 in water and neutralizing with KOH." Actually I obtained a white solid with a green/grey solid layer above it. How do I
get white crystals of Potassium Selenite? 
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fusso
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Filter out the insolubles before crystallizing the prodct.
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woelen
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You had impurities in one (or both) of the reactants.
Dissolve all of it in as little as possible of distilled water, measure the volume and double that volume. Next, filter, and then allow to evaportate
again. Allow to evaporate in a dry place, free of dust, but do not allow to evaporate to dryness. When 10% or so of the volume of liquid is left and
you have 80 to 90% of your solid again, then decant the liquid and dry the solid between pieces of filter paper. Let the solid dry further. This is
your pure crop of selenite and should be white.
The remaining part can be evaporated to dryness. This then is crude selenite, not to be mixed with the main crop. For some experiments, the crude
stuff is good enough, for more demaning and critical applications, use the pure material.
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rocketman
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Sorry but I don't understand part of the instructions.
Dissolve all of it in as little as possible of distilled water, MEASURE THE VOLUME AND DOUBLE THAT VOLUME. ? of water? KOH? Thank you.
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fusso
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Quote: Originally posted by rocketman  | Sorry but I don't understand part of the instructions.
Dissolve all of it in as little as possible of distilled water, MEASURE THE VOLUME AND DOUBLE THAT VOLUME. ? of water? KOH? Thank you.
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Water. You dont want extra KOH to contaminate your product. Best to have as little impurities as possible.
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