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I have a question regarding the solubility of baking soda (bicarb soda) in oil. I am pretty sure that it has poor solubility, but I have a chemistry dilemma and cannot seem to solve it.

I make all-natural deodorant, and the main ingredients are coconut oil, shea butter and baking soda (amongst a few other ingredients). We have been making it for years, and it was always soft and smooth, but this time the baking soda is not dissolving and leaves a gritty texture (even after sifting baking soda to remove lumps).

Does anyone have any idea why this might be? We heat the ingredients to melting point on the stove, then let cool to room temperature and re-solidify in the fridge for a day, before using.

The only thing I can think of is that we have recently changed to a new brand of baking soda; however, with adequate mixing, surely that would not change the final texture so much.

Thank you!

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  • $\begingroup$ Dissolve the bicarbonate in water first before mixing with your concoction. Add in emulsifier so that you get a nice single phase lotion. $\endgroup$
    – Paul Liang
    Commented Jul 25, 2021 at 10:10

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The baking soda grain size might be bigger in this new brand. When you sift, you break up individual grains that have clumped together due to moisture or being pressed together tightly but there is a fundamental particle size from how the baking soda was manufactured that would require further processing to reduce (e.g. milling). The larger grain size would adversely affect the solubility. It could also be that the baking soda you buy now is either missing some additives or has some additives that are detrimental to your final product.

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  • $\begingroup$ @EssElle Compare the ingredients list between the two brands to see if there is any difference, that may tell you the story from the additives side. The grain size issue would require a powerful microscope seeing as how baking soda is so fine. You could try running the baking soda you have now in a high power blender and see if that helps. $\endgroup$
    – J. Ari
    Commented Jun 3, 2017 at 0:56
  • $\begingroup$ @EssElle If my answer is satisfactory, please consider accepting it. $\endgroup$
    – J. Ari
    Commented Jun 3, 2017 at 0:58

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