zno and ph in a lotion

Good night, i am working on a lotion using 8percent or more zno. this zno is not coated with silica dimethicone or anything else. As i know the ph should be 7 or lower(5 or 6). I have used citric acid and metered the ph of lotion 5,7. 1 or 2 hours later i metered the ph of lotion 7,1. why it has increased. what should i do saving my zno becoming an anion. Please help me. I am accepting book suggestions of this topic too. Thank you a lot.
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Comments

  • I think Zinc needs to be above 7.
  • chemicalmattchemicalmatt Member, Professional Chemist
    That much ZnO will not be soluble in any workable amount of acid; which you may only use acetic or mineral acids (e.g. HCl, HNO3) anyhow, so give up on solvating it, just disperse it in oils or paraffinics like everyone else does. That way, your pH is irrelevant.
  • Yes i am dispersing in some parafins and oils as you say. If i do that way will not the zno be amphoteric. I want to adjust the ph below 7 at the end. when i want to adjust ph lower the 7, i need citric acid %2 and this makes the lotion more viscous.
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