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Name: Jacquie H.
Status: educator
Age: 50s
Location: N/A
Country: N/A
Date: 2000


Question:
A student asks "Wouldn't it be impossible to gauge the melting point of a diamond because it is so high, the equipment would be destroyed in the process?" I discoverd the melting point is over 3800 Kelvin but have no idea how this was arrived at. Can you help us?


Replies:
A very perceptive student!!! You are correct, the melting point of diamond at atmospheric pressure is the highest of all known materials, so its melting point must be measured under high pressure and the melting point at atmospheric pressure calculated from thermodynamics, which is quite reliable. At 1 atm the melting point is about 4000 K +/- ~200 depending upon whose measurements you believe. However, the melting temperature drops to about 1200 K at 600k-bar. Both of these conditions are attainable in the proper equipment.

You can find out the details at the following website. It requires Acrobat Reader.

http://www.nuc.berkeley.edu/html/academics/classes/E-115/Reader/chap6.pdf

Vince Calder



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