How to disperse salicylic acid in sodium lauryl sulfate solution? [closed]








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Anti-dandruff shampoo contains salicylic acid as an active ingredient, but when salicylic acid powder comes in contact with a base solution such as sodium laurylsulfate and water (1:3 wt/wt) caking of the particle occurs, forming a non-dispersible aggregate.


I know from the study of pharmaceutics that decreasing the *contact angle* between particles and solution leads to a decrease in surface tension and thereby dispersion of the particles.


How can one disperse the salicylic acid particles specifically in this base solution?




I don't have a lot of experience with salicylic acid as I'm just starting to work with it myself at the moment. However, I find that it disperses better if it is added to the solution at a high temperature (before surfactants) and then homogenised (once thickening agents, if any, have been added).


The other thing which may help is by dissolving in denatured alcohol, although I haven't personally tried this myself. Although it's not a shampoo, I have recently formulated a facial cleanser and as described above I firstly added the thickening agents to the water and then salicylic acid, heated to approximately $70~\mathrm{^\circ C}$ and then homogenised.


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