I'm looking for the least expensive method for making food grade zinc carbonate (for a molecular gastronomy recipe I'm developing). I know it can be done with the soluble forms of zinc (sulfate, chloride and possibly acetate) by combining them with sodium carbonate (which I have), but the highest purity I can get on sulfate is 99.3 and chloride is 97. Zinc oxide is relatively cheap, but the acids that will take me to either chloride or sulfate are way out of my price range. I use food grade citric acid as a component in my DIY dishwashing powder, but I don't see citric getting me anywhere in this quest. Vinegar and zinc seems like an especially weak reaction, and, when you get into pure acetic, it's just too much money. Zinc oxide and ammonium chloride, from small amount of research I've done, seems to get me to zinc chloride (and ammonia), and high purity ammonium chloride is relatively affordable, but I haven't come across a lot of information on this reaction. Is this is a strong reaction? Any help would be appreciated.