I am using 99% isopropyl alchohol to clean soldering flux residues for my electronics projects. Due to a certain viruse running amok in the world today, I am not able to get from my usual supplier. I am running low on supplies. So i got this idea that i would concentrate the more common (but still not so easy to get in my area) 40% or 70% ispropyl alchohol.

Searching the internet on guides to do it, it would seem that there is an easy way to do it. According to this instructables; add non-iodized salt to the solution until its past its saturation point. By this time the heavier water should sink and the lighter isopropyl should float. Extracting it would now be easy with a syringe.

For my question. Water and especially salt is an enemy to any metal. I would like to ask if this process mixes tiny amount of salt to the isopropyl? if so by how much %? Is NaCl even soluble to isopropyl or are these just tiny particles floating around and if i leave the solution to settle for a longer period of time those particles would sink down. up until what percent can i bring the concentration to?

As for the Salt to use what other ingredients should i look out other than iodine( or other close sounding).

P.S. I am no chemist any way, the only chemistry background i have is during my high-school days. It was a time that i was still not able to appreciate class lessons. So go easy on me

  • 4
    $\begingroup$ I've never heard of adding salt to create two phases between water and isopropyl alcohol, but if you want to create concentrated isopropyl alcohol I'd suggest distillation. The alcohol should distill off before the water. $\endgroup$
    – CH3M
    Mar 13 '20 at 19:07
  • $\begingroup$ Anhydrous magnesium sulfate would do what you want $\endgroup$
    – Waylander
    Mar 13 '20 at 19:10
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    $\begingroup$ Waylander & DrMoishePippik - Both of those salts are hygroscopic. That doesn't seem to be a good thing on a circuit board. $\endgroup$
    – MaxW
    Mar 13 '20 at 19:30
  • 1
    $\begingroup$ Simple distillation won't work. From Wikipedia "Isopropyl alcohol forms an azeotrope with water, which gives a boiling point of 80.37 °C (176.67 °F) and a composition of 87.7 wt% (91 vol%) isopropyl alcohol." // So you could dry over a salt, then distill to be sure that there were no particulates in the liquid. $\endgroup$
    – MaxW
    Mar 13 '20 at 19:48
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    $\begingroup$ Not a bad question, but all in all there is no "simple" way for a ordinary person without a lab to purify isopropyl alcohol. The chemicals and equipment needed will be a much greater expense than the isopropyl alcohol. Without a proper lab there is also a safety concern. Isopropyl alcohol is flammable. $\endgroup$
    – MaxW
    Mar 13 '20 at 20:53

Common table salt can have additives, so I would recommend working with high purity Epsom Salts (magnesium sulfate hydrate). Heat to remove water of crystallization at 100 degrees Celsius for two hours.

Add your isopropyl alcohol with the MgSO4 in excess and wait until there is a separation. I would decant and allow for a safety margin above the visible separation line.

Here is a reference.

  • $\begingroup$ would the isopropyl contain any traces salt after the process? $\endgroup$
    – Jake quin
    Mar 14 '20 at 17:48

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