# Purifying washing soda

I bought a box of A&H Washing Soda, the packaging of which implied that it was pure washing soda (sodium carbonate).

On dissolving it in osmotically-purified water, however, I found that the water took on a brown tinge, which would seem to indicate a contamination or adulteration of some type. Also, the washing soda tended to form hard chips or clumps, which I have not seen in previous experiments doing the same thing.

I suspect there may be some kind of organic compound being used to adulterate the washing soda.

How can I determine if there is an organic adulterant and remove it?

• In addition to the answer given by Curt: It might be interesting to see whether the same effect can be observed using destilled water, rain water or any (tab) water that didn't go through the RO purifier. – Klaus-Dieter Warzecha Mar 2 '15 at 11:10

If there is an organic contaminant in the $\ce{Na2CO3}$, you could try to rinse the sodium carbonate with an organic solvent in which $\ce{Na2CO3}$ is insoluble. Based on this paper, acetone and methanol would qualify. Since those solvents, especially methanol, are toxic, I'm not recommending either one of those. Based on the data for methanol and acetone, I'm guessing absolute ethanol would also be incapable of dissolving sodium carbonate, so it would probably the best (relatively) non-toxic solvent for extraction. If you can't get absolute ethanol due to tax or beverage laws, you could probably used denatured ethyl alcohol instead. It usually has small percentages of methanol, acetone, and/or isopropyl alcohol added to make it non-potable.