Rogeryermaw
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soxhlet help
i was taking my improvised soxhlet setup for a spin the other day. by improvised i mean, it is an equalized funnel over a boiling flask with a
condenser on top. instead of siphoning off the solvent, you open the valve. not as hands free as a regular soxhlet, but takes more affordable
equipment and does about the same job(thank you peach for the idea). i just wanted to tune my technique using it so i made a cotton plug for the
bottom, put some alumina over that(just to have some form of substrate), and sealed it in with a cotton plug over the top.
using petroleum ether(ligroin. about 100ml in 250 ml flask)i began the process and it reached boiling temp quickly. the solvent traveled as expected
up the equalization tube and condensed in the top and dropped down into the funnel. seemed to be working quite well.
problem was that as the pet ether began to dwindle down to about 15-20 ml, it just boiled and boiled but no more would condense and the volume in the
flask would not drop any further until i opened the valve. as soon as the solvent hit the boiling bath, fumes shot up into the condenser and started
dripping like crazy.
my question is, can anyone give me insight as to why the last bit of solvent would not evaporate? there was no where that i could detect any obvious
refluxing and there were no odors of solvent vapors escaping. when i did open the valve, the vapors never went higher than 1/3 up the condenser(liebig
by the way) before condensing so that part is pretty efficient. i am puzzled the eff out.
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hkparker
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How pure is your solvent? Perhaps there is something in there with a higher BP?
My YouTube Channel
"Nothing is too wonderful to be true if it be consistent with the laws of nature." -Michael Faraday
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Rogeryermaw
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that is a damn fine question. according to the msds for cas#8032-32-4 it is 100%. i have had it for about a year but the bottle has been sealed,
unopened in a refrigerator. given the nature of many chemicals and my luck, 100% may be a stretch but i doubt it was adulterated up to 20%. i say up
to 20% because that is the approximate volume of solvent that refused to cooperate.
the solvent bath never did stop boiling, it just did not evaporate, travel up and re-condense. this is the first time i have ever seen a fluid boil
without losing volume.
http://www.sciencestuff.com/msds/C2214.html
edit: added link to msds
[Edited on 26-6-2011 by Rogeryermaw]
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