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I have a solution of potassium dichromate ($\ce{K2Cr2O7}$) and I want to convert it to a less toxic solution. What would be the best way to do this?

I was thinking of using the dissolved potassium dichromate as an oxidizer in the oxidation of alcohols to organic acids, to eventually produce the chromium(+III) ion (what is less toxic)

Or are there any other, easier methods?

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>Or are there any other, easier methods? The cheapest and safest one is probably to use ethyl alcohol and some acid (acetic acid should work). – permeakra Mar 2 '14 at 15:39
Ethyl and any other alkohol is a bad idea. Reaction of chromate with alcohols is slow. Try FeII as Kwak recommends. – Georg Mar 3 '14 at 19:30
up vote 4 down vote accepted

That looks like one way to reduce the dichromate ion which is known to be toxic. MSDS sheets indicate that potassium dichromate has category 1B carcinogenicity.

Another way I believe is to just start from an aldehyde and convert it into a carboxylic acid:

$$\ce{3RCHO + 2Cr_2O_7^- + BH^+ -> 3RCOOH + 2Cr^{3+} + 4H_2O} $$

Alternatively, one can put dichromate in acidic solution with iron:

$$\ce{Cr2O7^{2-} + 6Fe^{2+} + 14 H^+ -> 2 Cr^{3+} + 6 Fe^{3+} + 7H_2O }$$

Dichromate oxidizes $ \ce{Fe^{2+}}$ ions and produces $\ce{Cr^{3+}}$ and $\ce{Fe^{3+}}$ ions.

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@tschoppi Thank you for the edits. I am still getting used to mathjax. – anosdsd Mar 2 '14 at 17:17
thanks! I'll use the iron oxidation method, however : would an acid such as acetic acid be sufficient for this redox reaction? – LievenB Mar 3 '14 at 7:33
@LievenB Hi, I believe so. As long as you have enough acetic acid to form a ratio of moles of 14:6:1, that would be sufficient for this redox reaction. – anosdsd Mar 3 '14 at 12:40
@LievenB No problem! My pleasure! – anosdsd Mar 3 '14 at 12:57
@Jun-GooKwak It's acceptable to flag those comments as non-constructive. Thanks for your patience. – jonsca Mar 4 '14 at 5:45

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