How to Determine the melting point higher than 100oC

Identicalsnow · Post by **Identicalsnow** » Tue Oct 12, 2010 2:50 pm

Could anyone please point me in the correct direction to answering this. This is my first year of Chem and I enjoy it very much but the instructor is poor on explinations. Science is my major but now I'm second guessing myself and getting confused with this course.

How can you determine the melting of a substance whose melting point is higher than 100oC?

expert · Post by **expert** » Tue Oct 12, 2010 11:27 pm

Use glycerol or silicon oil to go to higer temperatures. Check temperature stability of the oils before going to temperatures higer than 150C

Identicalsnow · Post by **Identicalsnow** » Wed Oct 13, 2010 4:27 am

Thank you.

So that would mean that the oil, because it boils at a much higher temperature than water, would hold in more heat allowing the 1-2mm of substance to reach it's 100oC melting point. Am I correct to assume and understand that?

Now I read that you'd do the same for boiling point as well, use an oil bath. When the substance reaches that point it would boil but the only indication of that would be the bubbles from the capillary tube.

So the same concept works for both types melting and boiling? I just want to make sure I throughly understand.

Appreciate the help,

Than you very much

expert · Post by **expert** » Wed Oct 13, 2010 11:02 pm

The reason for using oil or glycerol is just to achieve a higher temperature so you can run measurements at those high temperatures. Melting point can be measured very precisely at least for pure compounds. Boiling point can be only estimated by this method. Frequently you won’t see a difference between boiling and degradation.
Precise boiling point can be only measured by temperature of vapors during distillation.

Identicalsnow · Post by **Identicalsnow** » Sun Oct 17, 2010 8:37 am

Thank you very much Expert for the help!