Author Topic: ??Melt point How to??  (Read 2171 times)

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antibob

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??Melt point How to??
« on: April 27, 2001, 09:46:00 PM »
Well I am sure that this is old news to alot of Bees, but I have never done a Melt point test and I feel it is about time I put this technique to use, I dont have a Thomas-Hoover apparatus or a thiele tube, but one of my books covers it by melting the ends of some glass tubing and loading it with what to be tested and hooking your thermometer to the home made capillary tube and placing it ito a beaker with oil and heating it.  Sound right???

terbium

  • Guest
Re: ??Melt point How to??
« Reply #1 on: April 27, 2001, 11:08:00 PM »
That's it.

Chromic

  • Guest
Re: ??Melt point How to??
« Reply #2 on: April 28, 2001, 12:39:00 AM »
Use an oil bath with a good sample of the compound loaded in a perfume vial. This is a bit harder to run than a regular MP test, but quite accurate.

terbium

  • Guest
Re: ??Melt point How to??
« Reply #3 on: April 28, 2001, 12:53:00 AM »
But if you've got the capillary tubes then smaller is better.

antibob

  • Guest
Re: ??Melt point How to??
« Reply #4 on: April 28, 2001, 01:31:00 AM »
I dont have any capillary tubes but I took some maybe 4mm glass and heated the end to get it closed off..  What's a good clear oil??  An inpure sample will have a wide melt range and a pure sample will not have?? Thanks for your input..

terbium

  • Guest
Re: ??Melt point How to??
« Reply #5 on: April 28, 2001, 01:23:00 PM »

An inpure sample will have a wide melt range and a pure sample will not have??


Correct.


What's a good clear oil??


Crisco Oil, any safflower oil - just go to the grocery store and buy a liter of some likely looking cooking oil.


the_student

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Re: ??Melt point How to??
« Reply #6 on: April 28, 2001, 01:49:00 PM »

the_student

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Re: ??Melt point How to??
« Reply #7 on: April 28, 2001, 01:54:00 PM »
Capillary tubes are cheap and well worth getting. Using a capillary attached to a thermometer is fine if you don't have a professional device. I wouldn't use the oils recommended in this post for temps over 200 C. You can get silicon oils for that. Technique and a basic understanding of the theory are essential for using melting points as an analytical tool. Here is a link with some info, there are probably better ones out there but this one isn't bad. It has other info too.

http://orgchem.colorado.edu/hndbksupport/meltingpt/mtfill.html

..oh yeah..you might want to rig-up a magnifying glass to observe the sample so you don't go blind watching it melt  ;)

scram

  • Guest
Re: ??Melt point How to??
« Reply #8 on: April 30, 2001, 08:25:00 AM »
I did a MP test with the right equipment weeks ago testing mdea. I had know idea what to do but it seemed pretty foolproof to not understand it. However, I don't know what the results mean as far as purity. The mp of the crystal was between 166 and 172. Shulgin reports his as 202.

b159510

  • Guest
Re: ??Melt point How to??
« Reply #9 on: April 30, 2001, 08:44:00 AM »
Responding to:
However, I don't know what the results mean as far as purity. The mp of the crystal was between 166 and 172. Shulgin reports his as 202.
Flame, rip, etc...lol..Assuming all other variables can be eliminated ( 202 c is correct, technique good, thermometer accurate) the results indicate the product is far from pure. ...no further comment...