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I have worked in electronics and aeronautics industry 30 years ago, and I have always wondered, what were the specific properties of isopropyl alcohol, which make it used instead of other alcohols like common methyl or ethyl alcohol ?

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I know that it's less toxic than other solvent and that it is easier to separate from water (by adding salt) than other alcohols (reduce producing costs ?), but some reasons might be less pertinent than others.

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2 Answers 2

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From this Wikipedia article

Isopropyl alcohol dissolves a wide range of non-polar compounds. It also evaporates quickly, leaves nearly zero oil traces, compared to ethanol, and is relatively non-toxic, compared to alternative solvents. Thus, it is used widely as a solvent and as a cleaning fluid, especially for dissolving oils.

You should try Googling first :-)

Also, the antiseptic properties of isopropyl alcohol are an added benefit (over the other lower alcohols).

As you pointed out, methanol is notoriously toxic, so using that as an industrial cleaning agent is a no-no.

Ethanol for industrial purposes is often available as denatured alcohol; which has added impurities to render it toxic and/or alter its taste and smell. These impurities may interfere with the equipment (you mention the electronics and aeronautics fields) you clean it with.

However commonly available isopropanol isn't denatured (then again, there's no real need to denature it). Since it is lacking in added impurities, it presents itself as a better choice over ethanol for cleaning such equipment.

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  • $\begingroup$ I did it, but knowing some difference doesn't tell me which are the most pertinent for the choice. btw, I wonder why ethanol would leave oil traces. $\endgroup$
    – Camion
    Commented Jan 14, 2018 at 6:21
  • $\begingroup$ @Camion I've edited my answer. As for the bit on oil traces, both ethanol and isopropanol leave oil trace, but the latter less so (from the Wikipedia wording). I took the liberty of interpreting this as being indicative of most oils being more soluble in isopropanol than in ethanol (though I'm unsure why exactly this would be so) $\endgroup$
    – paracetamol
    Commented Jan 14, 2018 at 6:40
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    $\begingroup$ At the lab bench scale (like cleaning a microscope slide eg) one can use ethanol as well. berkshire.com/learning-center/dyk_1408_why_ipa $\endgroup$
    – Alchimista
    Commented Jan 14, 2018 at 10:11
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    $\begingroup$ >there's no real need to denature it || you are underestimating capabilities of human liver and needs of human drunkards. While not very common, the use of isopropanol to achieve drunkenness is known. $\endgroup$
    – permeakra
    Commented Jan 14, 2018 at 20:56
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    $\begingroup$ @Hashim I heard it repeatedly and talked to people who claimed to use it. Official data suggests that it is possible to drink small (<10 g) dose of isopropanol with no severe effects for health, and isopropanol does produce narcotic effects ncbi.nlm.nih.gov/books/NBK208299 (read carefully, it is well hidden in "effects on animals"). I have no idea how widespread this practice is. $\endgroup$
    – permeakra
    Commented Mar 27, 2018 at 9:57
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It depends on what impurities are being removed. Methanol, ethanol and isopropanol can be purchased or purified to equivalent degrees of purity. If they are used in a condensing vapor degreaser neither will leave an "oily film". Methanol removes ionics better, isopropanol removes nonpolar materials better. Alcohols aren't the best to remove greases [methylene chloride or trichloroethylene are best here], and nothing removes fluorocarbon greases. Safety and environmental concerns are addressed by good lab techniques. There is serious trend towards using water based detergent systems. Their inception can be problematical, and I sometimes wonder if their use is better for the environment.

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