Register to reply

Sublimation MP and VP

by morgan8222
Tags: sublimation
Share this thread:
morgan8222
#1
Apr7-12, 01:03 PM
P: 16
I am wondering if I can separate these two compounds:

Y: M.P.=170 degrees C - Vapor pressure at its MP = 0.05 torr

Z: M.P.=170 degrees C - Vapor pressure at its MP = 540 torr

I think having a huge difference in vapor pressures is good. I am kind of confused about this process.
Phys.Org News Partner Chemistry news on Phys.org
Water leads to chemical that gunks up biofuels production
Celebrating 100 years of crystallography
Turning waste from rice, parsley and other foods into biodegradable plastic
chemisttree
#2
Apr7-12, 01:27 PM
Sci Advisor
HW Helper
PF Gold
chemisttree's Avatar
P: 3,724
You aren't really subliming it if you do the process at or above the melting point. It is just simple distillation. You will need a really cold "cold finger" to isolate Z. I would finely grind it and put in into an ampoule. Pull a mild vacuum on the ampoule and flame-seal the ampoule. Invert the ampoule so that the sample is entirely in the upper bulb of the ampoule. Attach the ampoule with a clamp to a vertical riser being careful to hold it vertically so that all of the sample is still contained in the lower, bulb side of the ampoule.

Now the fun part... Place a puck of dry ice on the flat side of the ampoule and heat the bulb with something. You can use an oil bath, handheld bunsen burner or lab heat gun. I prefer the oil bath. Replace the dry ice puck often. You will notice a solid slowly build up on this side of flask. When you have enough, remove the heat and dry ice and allow the ampoule to come to room temperature. Snap off the top and the base should contain very pure crystals of Z. The bulb will be quite enriched with respect to Y but will be contaminated with some Z.

This is how we purify old ampoule samples of osmium tetroxide in the lab.


Register to reply

Related Discussions
I am wondering if this would work:I need to sublimate compound 1 Chemistry 1
Sublimation of ice Advanced Physics Homework 18
I can't figure out why this happens with pure substances. My book is a General Physics 2
Query about Sublimation Atomic, Solid State, Comp. Physics 3
Why substances can undergo sublimation and turn into gas? General Physics 1