[dumdum]

I want to make two different aloe vera topical "creams", one with potassium iodide and one with epsom salt (magnesium sulphate heptahydrate).

The aloe vera gel is 99.9% but has the following additives: Acrylates/C10-30 Alkl Acrylate Crosspolymer, Panthenol, Disodium EDTA, Sodium Hydroxide, Phenoxyethanol, Potassium Sorbate, Phenoxyethanol

When I added the epsom salt the gel turned back into a liquid, I've read the same happens with the iodide. Do you think there could be any chemical reaction I should be careful of?

Thank you

[billnotgatez]

As one who uses Epsom Salts in ceramics I have seen the following question and answer;
Why Use Epsom Salts in a Ceramic Glaze Recipe?
The main purpose of adding Epsom Salts to a glaze recipe is to keep the glaze in suspension.

The idea is that it does not change the chemical makeup, but the physical property of how the ions interact in a water solution.

So this could possibly be the cause, but there are so many other compounds in you cream I could not be sure of other possible interactions. Thus, I can not be sure there is a parallel reason for your situation.

[fledarmus]

Are you getting a clear homogeneous liquid? Or are portions of your gel separating out? Frequently in doing extractions, salts are added to break up emulsions. Your aloe vera gel is a stable emulsion - you may simply be breaking it by increasing the ion content.

Another possibility is your pH. The thickener that you are using, your C10-30 Alkyl Acrylate Crosspolymer appears to be Carbopol(R) 1342, from a quick google search. The viscosity of solutions of this compound is very sensitive to pH. See http://www.lubrizol.com/WorkArea/linkit.aspx?LinkIdentifier=id&ItemID=31936 for more information. Other technical specs for that compound are available here: http://www.lubrizol.com/PersonalCare/Products/Carbopol/1342.html

[dumdum]

Thanks for the responses.

After mixing it becomes a clear homogeneous liquid.

The aloe vera gel had stated it was "additive free" so I was disappointed to see all the extras to confuse things. I must apologise, all this sciencey stuff is a bit over my head but your answers do seem sensible and it doesn't seem to be much cause for concern.

[Extracted]

When I added the epsom salt the gel turned back into a liquid, I've read the same happens with the iodide. Do you think there could be any chemical reaction I should be careful of?

The thickness of the gel is coming almost entirely from the acrylates copolymer.  When deprotonated (by the sodium hydroxide in the ingredient list) these acrylates produce a clear gel.  They are used to thicken products like hand sanitizer, hand soap and shampoo.  Your epsom salt contains a divalent ion (Mg+2) that complexes the carboxylate moieties of the acrylates copolymer which destroys its ability to thicken.  The EDTA usually complexes these divalent ions but you just added too much epsom and overwhelmed it.  The same kind of thing happens to the carboxylate of castile soap where the magnesium ions (or calcium ions) in hard water produce a soap scum.  Somewhere in your sample you may have a precipitated form of the acrylates copolymer.   Not dangerous.