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I have a bottle of baby powder that is 15% Zinc oxide and the rest is talc. Is there an over-the-counter way of purifying zinc oxide from it? I'm trying to make some sunscreen from it.

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This might be not worth it, because you will need special equipment.

Description totally theoretical.

Mixture consist of $Mg_3Si_4O_{10}(OH)_2$ - tale powder, $ZnO$ - zink oxide powder, and starch. 81% to 15% to 4% it's most common variation with 15% zink oxide, there also 10% mixtures, but process will be the same.

  1. You need to get rid of starch. Best choice to convert it to dextrine, because starch in not fully soluble in water. You need to heat it in oven on a foil for about 2 hours, with temperature $200^{\circ}C$. It will have no effect for other components, zync oxide might colorize to orange, but when heat is gone it will be white again. Dextrine will be yellow color and it's fully soluble in water.

  2. Mix new mixture with water, and pour it out. Now you have only $Mg_3Si_4O_{10}(OH)_2$ and $ZnO$ in you mixture. Both of them not soluble in water.

  3. Then you need to obtain or build equipment for sublimation - sublimation apparatus. Because compounds have different melting point Talc - $800^{\circ}C$, zync oxide - $1975^{\circ}C$, you can get them one by one. You will need to freeze and dry your mixture first.

  4. Heat over $800^{\circ}C$ to obtain talc, left over structure will be zinc oxide.

I'm not sure about sublimation from start, with starch inside, but this method in theory should work.

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  • $\begingroup$ It sounds great till the 800 degrees part. Could I potentially throw it all in HCL and then into sodium carbonate solution? Or will I get some magnesium oxide from the talc as a result? $\endgroup$ – Alex Jun 26 '13 at 6:48

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