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Author: Subject: Vaccum from Aspirator
zenosx
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[*] posted on 19-10-2014 at 17:08
Vaccum from Aspirator


This was such a newb question I stuck it here in beginnings.

So during my benzyl chloride vacuum distillation I observed the primary fraction coming over @ ~ 80°-82°C. For the second fraction I observed ~ 96°-99°C and third fraction at ~112°-120°C. (3rd was possibly just me increasing the heat to speed up the distillation as it was not coming over very quickly anymore.)

From the starting reaction there were only 3 possible fractions (not counting side reactions)
Benzyl Alcohol - BP:205°C
Benzyl Chloride - BP: 179°C
Water - BP: 100°C
HCL: (would have left quickly)

That is probably too much data but my question is, I am trying to determine my new aspirators vacuum supply. Very loosely going from my nomograph I predicted ~ 20 Torr on the first fraction of 80°C.

Does this sound reasonable or am I wayyy off..for an aspirator. There is so much crap out there and so many wildly fluctuating figures I figured I would ask for my setup.

Thanks for reading this long post...




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[*] posted on 20-10-2014 at 07:14


My aspirator gets down to 50 torr pretty reliably, but no lower. The theoretical minimum for an aspirator is about 18 torr, assuming 20 C water.



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zenosx
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[*] posted on 20-10-2014 at 17:42


Well I was using my nomograph taped to the wall near my lab and an inoculation loop as the key.. so there is a large margin of error.

I am using a new nickel aspirator that I just installed, and 50 torr max sounds reasonable. Thanks for the input.

IMHO that is still a respectable vacuum to be had from an aspirator....




A question that sometimes drives me hazy: am I or are the others crazy?

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zenosx
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[*] posted on 20-10-2014 at 17:45


I think I'll do a control test of water BP and see what I get. I had just installed this source and needed to distill this high BP solvent/reagent. I have so little lab time that it literally took 4 weeks to just get time to distill the reaction product...



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