Quince
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Varying concentration of solution of salt without wasting said salt
Say I have a large amount of potassium thiocyanate solution, and I want to vary its concentration over some range to match refractive indices of
various glasses. Now, lowering the concentration by addition of water is simple, but increasing it without wasting the salt is a problem. How can I
do it? Evaporation is not practical in my application for various reasons, including the size of the setup. What drying methods are likely to work?
Would the use of something like diatomaceous earth molecular sieves work, or are the salt molecules not small enough for this to work? What other
options do I have, where the drying agent can be recycled?
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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azaleaemerson
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The idea that pops into my mind is making up a teabag of dried silica from the hobby store. The water should stick but not the salt.
Az
azalea
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unionised
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Stick the cold end of a peltier cooler in it and freeze out the water?
The trouble with drying agents like SiO2 is that they carry quite a lot of the salt solution trapped between the particles.
Depending on what you are doing you might be able to use a density gradient; high concn at the bottom- low concn at the top.
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mick
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I do not think you have many options. If you start of with a standard solution you can only dilute.
mick
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Quince
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So a molecular sieve won't work here? They seem quite often used for drying ethanol.
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mick
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If you manage to concetrate a standard solution under guaranteed conditions let me know
mick
edit spelling
[Edited on 17-10-2005 by mick]
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Quince
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It's not standard, it's solution on the order of 65%-70%, which matches the refractive indices of most glasses. I need to be able to match
different glasses, in any order, so I need to be able to have multiple dilutions and concentrations. I'm using about 3.5 L of the solution, and
I need a way to minimize the loss of the salt.
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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mick
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[Edited on 18-10-2005 by mick]
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epck
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Have you thought about reverse osmosis? You'd need a pump and a good membrane but that might be the fastest way of removing the water.
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Quince
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Interesting. Where to find a membrane? Do they last long?
Also, someone said rotary evaporator. But they are usually for smaller amounts of liquid.
I guess I could make up several different concentrations and switch between the solutions. But then I'd have to get several times the amount of
potassium thiocyanate.
[Edited on 18-10-2005 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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