Sciencemadness Discussion Board - Making a fractionating column

Making a fractionating column

Runningbear - 4-10-2009 at 19:11

I'm thinking of making a fractionating column out of three 12.5 cm 24/29 adapters. The plan is to stuff the bottom with glass wool and then fill it with grass boiling beads. I will seal the joints with grease and also a bit of teflon tape to ensure they are fully sealed, then add some type of insulating material.

The active fractionation length will be about 32cm but not very wide. Will this work?

Are there any other options for jerry rigging a fractionating column without having to buy one?

Thanks in advance?

Runningbear

Picric-A - 4-10-2009 at 22:57

I made my own fractionating column. I had a spare air condensor and i filled it with lots of bits of smashed pyrex (boror glass). I didnt seal the glass in so if you invert it the pieces will fall out through the top but its stable at the bottom (hole too small to let glass fall through)
It works like a charm, distillation of wine yielded around 80% alcohol by hydrometer.

JohnWW - 5-10-2009 at 00:02

Such an improvised air-cooled condenser, made from borosilicate glass adapters jointed together, would probably work, if air temperatures are cool, the glass column is long, and/or you could provide extra forced-draft convective cooling using a fan. Of course, because of the lower heat-transfer coefficients involved, the cooling of vapors is much less efficient than with a water-cooled condenser (either a water jacket around the column, or a coiled tube inside it).

The joints would need a fairly viscous grease that can withstand the expected temperatures of the vapors; either proper vacuum stopcock grease, or at least high-viscosity automotive grease. Stuffing the column with broken glass or glass boiling beads, held in place with glass wool at the bottom, would provide increased surface area on which vapors can condense; BUT it may unacceptably impede the gas-phase flow of vapors into it.

For an even longer air-cooled condenser, you could look at buying a length of glass tubing about 20 or 25 mm in diameter, supported by clamps, plus some rubber or flexible plastic tubing of similar diameter, and use the latter to join the glass tube to the outlet of the flask.

entropy51 - 5-10-2009 at 15:07

If you stuff in enough glass wool to reliably hold the glass beads it may prove too much of a resistance to vapor flow. Or cause the column to flood with liquid. Not enough glass wool and the beads will fall into your distillation.

After trying this and having problems I smashed a clay flower pot and selected a piece that would catch in the bottom of the column and yet not stop it up. The clay has held up to organics and acetic acid without problems so far. A coil of nickel foil also worked.

Glass rings are easier to support than beads since they won't fall through a small opening as easily.

Picric-A - 6-10-2009 at 01:52

I have in my lab a bin dedicated to smashed glass. This was invaluable when i decided to make my column becuase i had a source of highly chemical resistant packing

entropy51 - 6-10-2009 at 05:33

Quote: Originally posted by Picric-A

I have in my lab a bin dedicated to smashed glass.

How big is that bin, anyway?

I was going to say that I never break anything so I had to smash a flower pot. But I dropped a graduated cylinder the other day. First thing I can remember breaking this century.