From: William Levak (wlevak_at_grex.cyberspace.org)
Date: 2005-06-22 20:18:46
It has been said here, and other places, that if you buy Isopropyl
Alcohol, and the label on the bottle says "Rubbing Alcohol", that means
that it contains 1 per cent mineral oil.
This is nonsense!
Being a chemist myself, I can tell you that the terms "rubbing alcohol"
and "isopropyl alcohol" mean exactly the same thing. In the off chance
that pharmacists do things differently, I asked my local pharmacist. He
agreed with me.
I can also tell you that, by law in the United States, ingredients must be
listed on the label. If it does not say that it contains mineral oil on
the label, it does not contain mineral oil.
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The usual concentration of isopropyl alcohol is 70 per cent in water.
This makes a good cleaning agent for many things that do not come off in
water alone. The drawback is that it will leave water behind when it
evaporates, not a good idea on circuit boards. For circuit boards, 90 per
cent isopropyl alcohol is better. It will not leave water behind, and
will actually remove water. This is because 90 per cent isopropyl alcohol
is above the azeotrope of 78 per cent. ( I throw in that big word because
I spent a lot of time and money learning enough chemistry to know what
that means, and I occasionally like to get some use from it. )
For things that do not come off in isopropyl alcohol, lighter fluid is a
good bet. It is a light petroleum fraction and makes a good non-polar
solvent, while isopropyl alcohol is a polar solvent. ( These some are
more of those chemical terms. )
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OK, chemistry class for today is dismissed. You can return to what you
were doing before.
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