Chromatography Forum

Question: our lab is currently developing a method to distill used solvent into usable clean recycled solvent. We have a large still capable of holding about 45 liters. Up until now we have been testing 1) methylene chloride alone, 2) hexane/acetone alone. The current mix contains hexane, acetone, methylene chloride, and just a little bit of water. I have been going over azeotropic data and we expected to see methylene chloride/water mixture distilling around 38C, however the still temp jumps up past 45C almost right away, water still present in the mix, so we're stumped as to the makeup of what's distilling. Anyone have any knowledge of complex systems like this or know where I can find azeotropic data for this?

The CRC Handbook of Chem & Phys. 59th Ed. 1978-9 has 44 pages of azeotrope tables for binary and ternary systems. However, no source reference is quoted.

Another possible source would be,

Kirk-Othmer Encyclopedia of Technology, a multi-volume set that a university or large company library may have.

Is treatment with a drying agent (anhyd. Na2SO4) prior to distillation an option ?

I agree. Add sodium sulfate anhydrous and stir.

Thank you for the info I will definitely check into it. We do have the option of using sodium sulfate to dry the solvent, but when looking at the data we have about a system with dichloromethane, water, hexane, and acetone, we figured we'd simply be able to distill off the water/dcm portion, then dcm only, then hex/ace, then any remaining hexane (after hex/ace azeotrope finishes). We did not expect to see the temp fly up past the dcm/water boiling point. Thank you again, we will certainly have to employ a drying step to make things easier.