I asked my tame chemist in the office next door. I'm told if you add a
small amount of saturated salt solution, the oil should float to the
To make a sturated salt solution, dissolve as much salt possible into
hot water and let it cool so the excess solidifies out.
Let us know if it works.
That should work, though how much is a "small amount" I have some
reservations. Could get expensive.
"Salting out", as it is known, is a familiar technique in organic
chemistry for helping to separate water from organic liquids (which
frequently are able to dissolve significant amounts of water. It relies
on the fact that the solute reduces the free energy of the water - makes
it more stable - so less likely to bunk off into a misalliance with the
Trouble is, to be really effective, it needs the salt to be present in
fairly significant concentration, which would be expensive, and could
only be done by putting the salt in the coolant, not by adding a little
brine to a lot of coolant.
BTW, you wont get much more salt into water by heating it, the
temperature coefficient of solubility of sodium chloride is very low. It
will dissolve a bit quicker though.
You'll just have to try it; I don't use soluble (emulsified) oil myself,
I am speaking from experience doing organic chemistry...
OTOH, wouldn't it be easier (and cheaper) just to leave it in an open
container and let the water evaporate?
My thanks to all for the suggestions. Most of the flocculants appear to
present a bigger disposal issue than the coolant. I'll try the salt.
I have tried natural evaporation and that halved a 2 gallon bucket in 4
I'll give more thought to forced evaporation but volatiles might be an
again my thanks
An oil layer does indeed inhibit evaporation - markedly. I did a 3-month
test a year or so ago with a 5mm layer of motor kerosene (diesel) above
an open measuring cylinder of water. Evaporation of the water was
reduced by a factor of about 60 compared with unshielded water.
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