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After a solvent evaporates off of a surface there's always some residue left in the form of a strain.

Why it is the case even for highly volatile solvents such as acetone, toluene etc?

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  • $\begingroup$ I don't experience this with dichloromethane. Ether can leave a little water, maybe, but I haven't noticed that, either. Maybe it's the quality of chemical you're using? Of course, wash acetone is often lower quality, and I definitely wouldn't call toluene highly volatile. It probably has some petroleum contamination most of the time, too. $\endgroup$ Apr 22 '16 at 22:19
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If the surface material is clean and neither soluble nor reactant in any way with the solvent, then it is probably a solvent purity issue. If you have a good micro-balance, you could pour a known volume of the solvent into a pre-weighed light-weight, i.e. aluminum foil, container, dry it, and re-weigh. From that you can calculate the non-volatile solids content of your solvent and compare it to the specifications.

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The most common reason why evaporating solvents leave a residue is because they are good solvents and some of the surface or contaminants on the surface are dissolved in the solvent. This is very common for most non-inert surfaces with solvents like acetone.

Another explanation when the surface is very unreactive (glass for example) is that the evaporation of a volatile solvent cools the surface and causes other things (like water vapour) to condense onto the surface. This is certainly true for dichloromethane and ether which are so volatile that evaporating a large amount can freeze nearby water.

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  • $\begingroup$ Just 1 nitpick to what I think is otherwise a good answer: your first sentence says "...some of the surface or contaminants on the surface are dissolved in the solvent.". This certainly explains the appearance of what looks like a residue, but is another phenomenon entirely, and is not actually a process of leaving a residue from the solvent, as stated earlier in the sentence, "...evaporating solvents leave a residue...". While that is a bit of a nitpick, I think that it kind of confuses the issue of the question, whether the solvent is leaving a residue. Still, +1 for the answer as a whole. $\endgroup$
    – airhuff
    Feb 24 '17 at 21:20

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