Syn the Sizer
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sodium or potassium dichromate.
Hello, I am looking to purchase a dichromate salt and was wondering if there is a major difference between potassium and sodium dichromate. Is one so
much more effective than the other? The sodium salt is $38/500g and the potassium salt is $25/250g
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j_sum1
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Yes. There are big differences. Sodium dichromate is more than an order of magnitude more soluble in water than potassium dichromate. (I found this
out the hard way.)
This might not be significant for some applications, but if you are using it in a concentrated solution as an oxidant and your goal is to add a
certain number of moles to a flask, then a factor of 10 in the volume added is important to appreciate.
You don't have a big difference in price -- I would go for the Na salt without hesitation under those circumstances. My experience is the sodium salt
being more than double the price.
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Syn the Sizer
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Awesome, thanks for the feedback. That was very helpful.
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j_sum1
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No problems. 
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Tdep
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The sodium salt is hygroscopic though so doesn't store nearly as well as the potassium salt, if you're planning to use it over a long period of time.
Potassium dichromate stores very easily and indefinitely I believe
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woelen
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I personally like potassium dichromate more than the sodium salt. It is anhydrous, the sodium salt is a dihydrate. For some experiments with solid
anhydrous compounds the dihydrate can be a nuisance. An as Tdep mentioned, the sodium salt is hygroscopic. It is so hygroscopic that it becomes a wet
mess quickly when humidity in the air is high (e.g. on hot summer days in the dutch sea climate).
I have both salts, and they complement each other. Since the time I have CrO3, I hardly use the sodium salt anymore. If I want a high concentration of
oxidizer, then I take some CrO3, and for other purposes I take K2Cr2O7. CrO3 also is very hygroscopic, even more so than sodium dichromate.
If you can afford, try to get both salts, or try to get K2Cr2O7 and CrO3. A quantity of 500 grams is a lot, can't you get 250 grams for a lower price?
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Syn the Sizer
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Quote: Originally posted by woelen  |
If you can afford, try to get both salts, or try to get K2Cr2O7 and CrO3. A quantity of 500 grams is a lot, can't you get 250 grams for a lower price?
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The next below is 100g for $15, both the sodium and potassium slats are 100g for $15. The sodium salt doesn't have a 250g size.
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woelen
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I would go for 250g of K2Cr2O7 and 100g of Na2Cr2O7.2H2O. Then for $40 you have both.
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Syn the Sizer
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Perfect, thanks for the advice.
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