Solubility of NaCl & Sucrose in ethanol

One of the questions in my 15-year-old son's chemistry textbook asks, "How
would you separate [solid] sodium chloride and sucrose using the solvent
ethanol". The answer I think they want is that you dissolve out the sucrose
with the ethanol, which is subsequently evaporated off. I suspect this is an
error - I've already spotted a couple of others - because the book states a
few pages earlier that sucrose is soluble in ethanol. Data in Beilstein and
the International Critical Tables suggest that the solubility of sucrose in
anything like pure ethanol is very small. Comparison with solubility data
for NaCl from Linke suggests that the separation as described is impossible.

Has anyone any experience of the solubility of sucrose in ethanol or, more
likely, in denatured ethanol (industrial methylated spirits)?

How would *you* separate solid sucrose and NaCl? I favour some sort of
density separation, based on a heavy liquid with a density around 1.8 g/cm3
(CCl4 with a little CH2I2?)

Has anyone any wacky ideas for actually using ethanol as the separation
medium? (Countercurrent separation, again based on the density?)

"ebeveridge" <[Only registered users see links. ].uk> wrote in message news:<3f81d3e7$0$17375$[Only registered users see links. ].u k>...

You're saying, that NaCl _also_ is soluble in ethanol.


Not me, kemo sabe :-)


Personally, I'd throw the mixture away.


Get drunk. Put the mix in your mouth
and spit out the salt (or sugar).


Mark (...and for this, I should only get $350K a year?)

"ebeveridge" <[Only registered users see links. ].uk> wrote in message
news:3f81d3e7$0$17375$[Only registered users see links. ].uk ...
sucrose
an
a
and
in
impossible.
g/cm3
Both sucrose and salt are described as practically insoluble in ethanol.
However at high temperature - near the boiling point - things may change.
Also depends whether you're using pure "100%" ethanol or 95% ethanol, or
even weaker. May be room for some "suck it and see" with sucrose and salt
separately. Heating and cooling may lead to selective recrystallisation of
one compound.

Following your idea of density separation, maybe if you shake the suspension
the salt crystals separate really quickly and the sucrose is suspended for a
while.

Are you supposed to end up with only a tiny bit of pure salt + a tiny bit of
pure sucrose, or do you have to separate effectively the whole lot - a much
bigger challenge.

HTH

Barry Hunt

No, I didn't mean to imply that NaCl is soluble in ethanol - Linke gives the
solubility as about 0.06 %. I think the whole question is a load of crap,
based on a false premise - but I'm only 99 % sure of this, and I wanted to
see if anyone knew something I didn't.

"ebeveridge" <[Only registered users see links. ].uk> writes:

I can't answer your question, but am posing another for the group:-

Suppose I had one litre of a saturated solution of NaCl, then added a
tablespoonful of sugar to it, and stirred. Would the sugar all dissolve,
regardless of the salt present? Would any NaCl be forced out of solution
by sugar going into solution?

As for making use of the ethanol? Add some spring water, a few lumps of
ice, and sip slowly while stirring the vessel above. :-)
--
John Savage (news address invalid; keep news replies in newsgroup)

"ebeveridge" <[Only registered users see links. ].uk> wrote in message news:<3f81d3e7$0$17375$[Only registered users see links. ].u k>...


Using an ethanol powered torch, burn the sugar to completion. What's
left over is salt.

I'm not sure this is the solution your textbook editors had in mind,
but at least it allows you to recover all that valuable salt.

Dave