Author Topic: Fraction Cutter Wisdom  (Read 1767 times)

0 Members and 1 Guest are viewing this topic.


  • Guest
Fraction Cutter Wisdom
« on: October 01, 2002, 01:59:00 AM »
Cl's new fraction cutter is a real delight. Nothing like having a 100 ml scale on your fraction so you can tell how much your getting. Pix may follow of the setup...however, there are a few points that will save folks some pain when using these goodies...

  Whilest doing a fractional distillation w/ fraction cutter....

1.)  Test system prior to adding essential oils/reagents. Press on valves and check the gauge...make sure it doesn't change pressures...

Aspirator is pulling 760-700mm = 60mm according to gauge.

2.) Don't try and make your system "more tight" by mucking with joints while fractionally distilling.  The sudden increase in vacuum will cause all your goodies to blow through your column, into your condensor, into your receiving flask, and down your aspirator!

3.)  Do NOT close off the top valve to the aspirator/vacuum source when changing fractions. This causes the the vapor to build up pressure, increasing temp in boiling flask.  When you change flasks and then open the top valve, the sudden reduction in pressure causes all of your material to flash through your column, condensor, cutter, receiving flask and down the aspirator  :(

4.) Do drain your fractions regularly. A little of the good stuff is better than dumping it in all over again...

5.) Pay attention to the pre-run... Pre-run's always exist, product greed is just contaminated fractions, and you get to do it all over again...

6.) Use lots of silicone vacuum grease on your valves!  this made the difference between 645mm and 700mm in vacuum.
Nothing more disconcerting than to see a tiny stream of bubbles coming from your lower valve into your final product!

   Well, lots of fun, took a long time to get right... but wow... what a nice tool...

Infinite Radiant Light - THKRA


  • Guest
« Reply #1 on: October 01, 2002, 02:08:00 AM »
Yes, this we want pictures of - what style/brand of fraction cutter? When you are talking about the vacuum being 700mm, are you thereby saying that you have standard pressure (760 mmHg) minus 700mmHg, thereby achieving an absolute pressure inside your apparatus of 60 mmHg (torr)?


  • Guest
« Reply #2 on: October 01, 2002, 02:23:00 AM »

 I'm using an automotive gauge as my expensive 5 scale digital only starts working at around 15 torr, took a while to get my head around the inverse pressure.  Brand is a Kontes. Pix's in digital camera, I'll post them as soon as I upload them..

Infinite Radiant Light - THKRA


  • Guest
« Reply #3 on: October 01, 2002, 05:34:00 PM »
Here you are...

Setup for fractional distillation. This required wrapping the hotplate stirrer and the column w/ glass wool and aluminum foil to support temps.

Next is the kontes fraction cutter:

Top Valves: The top one controls vacuum to the system. The bottom one has a hole drilled through the center. This allows either full vacuum when aligned with the glass stem, or release to atmosphere when rotated 180 and the hole through the side into the center to atmosphere connects the bottom tube to the receiving flask.

Detail of bottom valve that releases the fraction from the graduated cylinder into the receiving flask. Note SS keck clips ( thx osmium!) on flask.

Detail of automotive vacuum gauge showing 26 in/ 650mm on the dial. This was prior to regreasing the valves which improved the vacuum to 700mm pull, 60mm actual.

Infinite Radiant Light - THKRA


  • Guest
« Reply #4 on: October 01, 2002, 07:14:00 PM »
Pre run issues were solved via recrystallization. The contaminated prerun was placed in the freezer along with the center fraction of saf.  The saf. froze, the prerun fraction was still liquid at -15F.

  A small crystal of saf. was removed from the flask and dropped into the prerun... a beautiful frost-like spreading soon consumed all but about 5ml's of the contents of the flask...

  No need for 2nd fractional distillation now... plus, small 1ml vial of ketone now in freezer for future seedings..

Infinite Radiant Light - THKRA


  • Guest
Can I Make A Few Suggestions?
« Reply #5 on: October 02, 2002, 12:33:00 AM »
Nice setup and pics, btw. Is that a Vigreux Column or Hempel, or??
I have found a great method of insulating my Distillation Columns. Go to the big Hardware store, plumbing section, and get a roll of Adhesive backed Foil Tape, and a section of Fiberglass Pipe Insulation. This insulation comes in 3 foot sections, and has a Foil/Paper backing. It's meant to "wrap around" water heater pipes, etc. There are different inside diameter openings, so measure the diam. of your column before  buying.
Now, wrap the whole column from top to bottom with pieces of the adhesive Foil Tape.(NOT the male GG joint though!) You might need 2 layers - the idea is that you want the fiberglass insulation to fit tightly around the column. Next, measure Fiberglass insulation to proper length and cut with a sharp knife. Put Column down center, and tighten paper "flap" so insulation stays in place.
Next wrap the outside of the insulation with another layer of the Foil Tape. Cut some smaller pieces if you like, to cover the 2 ends of the insulation where the fiberglass is exposed.
Now you have a column that has a layer of foil, a layer of fiberglass and foil, and another layer of foil over that!
I've found with this setup that I don't even need to insulate the Stillhead. And it's much neater than the loose fiberglass "wool".
If someone can tell me how, I'll post some pics of this.

If they drive God from the earth, we shall shelter Him underground - Dostoevsky


  • Guest
yeah, swims gotten safrole/iso to freeze out of ...
« Reply #6 on: October 02, 2002, 12:39:00 AM »
yeah, swims gotten safrole/iso to freeze out of dirty ketone, but never any of the yellow stuff.  First time, if its in the freezer, everything 'freezes', but thats just 'cause the good stuff is trapped in there.


  • Guest
re: ketone...
« Reply #7 on: October 02, 2002, 01:10:00 AM »
Err...saf.  I'm a few steps ahead in my brain than where these pics are...thx MM for the correction, I edited the post..

Infinite Radiant Light - THKRA


  • Guest
« Reply #8 on: October 02, 2002, 01:28:00 AM »
where I live, they don't carry pipe insulation cause it never gets that cold, but an excellent idea, I've even thought of getting heating tape and wrapping the column with that as well...

re: condenser. Well, it's sort of a vigurex, except imagine that the glass was clay and you squeezed it with your fingers putting hemispherical indentations 1/2 the dia. into the glass wall. Opposite each plate is a "thorn" of glass with it's tip set to drip at the top 1/4 of the bubble. It probably has some interesting theoretical plate number, and my more knowledgable glass blowers and chemist friends had never seen anything like it. It does a great job on separations however, and the price was certainly right.

Infinite Radiant Light - THKRA


  • Guest
"Anschütz-Thiele Vorstoss"
« Reply #9 on: October 02, 2002, 07:12:00 PM »
What is he talking about I thought reading the first post of CL and before my inner eye pictures of highly sophisticated electronic controlled devices appeared....

And now it is a "Anschütz-Thiele Vorstoss" !

I just don´t understand how a fractional distillation under reduced pressure may be made without a cow or this?

OK, fraction cutter is more at the point, but organic chemistry is german.
more or less.  :)


the column you describe is pictured in a czech glassware catalogue I have somewhere. I´ll try to dig it up if there is interest, was not very expensive as I recall....

~ Love is the law, love under will. ~