Yttrium2 - 6-6-2018 at 08:23
The thiele tube with a glass capillary was the old way of determining boiling point?
I have also seen an aluminum block on a hotplate with a small hole with a thermometer inside of it, the compound was placed on the plate, under
microscope and heated till melting.
Is the second way a viable way of checking melting point?
Are there any other, ghetto -- for lack of better terms, ways to determining melting point.
Lastly, are there any additional factors that affect melting point vs boiling point. I.E. if there is a mix of substances, do I go by the same rules
that affect the boiling point for mixtures? Ahhh
LearnedAmateur - 6-6-2018 at 08:37
Can always make a makeshift Thiele tube using a test/boiling tube with a holed bung, and the sample secured in a tube tied to the thermometer within
oil. The tube is held at a 45 degree angle for best convection, using a stand and clamp to hold it in place. Won’t be as accurate but should get you
to within 5-10 degrees if temp is increased slowly.
[Edited on 6-6-2018 by LearnedAmateur]
Ubya - 6-6-2018 at 08:41
mhh you mean melting point right?
anyway, the second option would be viable if you could really slowly increase the temperature of the hotplate, otherwise the melting range would be
really imprecise.
any other ghetto ways, well anything that can heat a sample slowly is ok, the important thing being able to measure accurately the temperature, so a
good thermometer is mandatory.
Yttrium2 - 6-6-2018 at 10:02
I'm kinda confused. In the video they heated a thiele tube with a Bunsen burner,
Why again does it need to be heated slowly? Won't the heat rise slowly as the oil heats up?
LearnedAmateur - 6-6-2018 at 10:28
Because you can easily overshoot the mark and get a funny reading with a flame burning at 1000C+, plus it will take a while for the oil to cool back
down again. The best way to take a M.P. measurement is to slowly heat so the temperature increases a few degrees a minute, mark the temperature when
it begins to melt (you’ll see it at the bottom), then take a second reading when it has completely melted for a range - one can assume that in most
instances, the narrower the range, the purer the product. Simply put, tightly controlled temperature will give a more accurate reading and will be
faster.