I am trying to make a mixture of the following ingredients: distilled water, alcohol, aluminum sulphate and glycerin.

The problem is that when I add alcohol to the water and aluminum sulphate mixture (the aluminum sulphate is completely dissolved), the alcohol solidifies the aluminum sulphate again, so I am left with even more solid aluminum sulphate then in the beginning.

What I need is for the mixture to be completely mixed, clear and without solids.

Thank you everyone for your time!

  • $\begingroup$ What's the solubility of aluminum sulfate in the solvent system you want? It may not be fully soluble. $\endgroup$ – Zhe May 21 '18 at 18:28
  • $\begingroup$ Do you have access to an ultrasound bath? $\endgroup$ – Waylander May 21 '18 at 18:51
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    $\begingroup$ An ultrasonic bath can help a soluble solid dissolve more quickly. In this case however, the OP has demonstrated that the solid is insoluble in the water alcohol mixture and nothing is going to help dissolve the solid in this solvent other than possibly changing the temperature. $\endgroup$ – airhuff May 21 '18 at 22:08
  • $\begingroup$ I don't have access to an ultrasound bath unfortunately. I did however try mixing the ingredients at high temperatures, but as soon as the mixture cools down the same thing happens... $\endgroup$ – Stefan May 23 '18 at 16:50

It looks like you added the alcohol before the glycerin. Possibly the aluminum sulfate would be more soluble with the glycerin in there, so try adding that before the alcohol.

Wikipedia calls aluminum sulfate only "slightly soluble" in alcohol, so the alcohol addition would be expected to lower the solubility of the salt. Nothing is reported there about the impact of glycerin.

Upon further review

Nope, we now find this did not work. Hence as other answers indicate, we need a more careful approach.

  • $\begingroup$ I tried this, it didn't work. The glycerin changes nothing, no matter how when or how much I put in. $\endgroup$ – Stefan May 23 '18 at 16:46

The solution occurs extremely slowly, but the ACS has an article on dissolving it by putting ethanol and aluminum sulfate (or aluminium sulphate, if you prefer, but aluminum sulphate would be a joint UK/USA contrivance) in a blender for five hours (!), then adding water. This procedure produced between 1% and 2.9% by weight $\ce{Al2(SO4)3}$ in $\ce{C2H5OH}$.

N.B. The friction of stirring and heat from the motor might volatilize enough $\ce{C2H5OH}$ to catch fire, particularly with sparking from brushes in the motor. Perhaps a hood with automatic fire suppression might be a safe place to try this... but I would be concerned even then. And this should be watched, despite the incessant noise of the blender!

  • $\begingroup$ Thanks for the input, but blending for 5 hours does not seem as a very practical way of getting what I neeed. $\endgroup$ – Stefan May 23 '18 at 16:47

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