From: Shu-Kun Lin (lin$##$mdpi.org)
Date: Sat Mar 11 2000 - 17:12:15 EST
Your first and the last questions (I reproduced at the the end)
are very much related, one is crystallization, the other is
its reverse process. These bothered me a lot too when I was
a student. Yuehui Zhou is right, you cannot find any of its
satisfactory theoretical explanation in any textbook. During recent 10 years I
spent almost all of my weekend time on this problem. "Successful"
theoreticians call it (crystallization) self organization. Their new
theories only messed it up and useless to me as an experimental
chemist. If you do not mind, you may find my explanation at the
http://www.mdpi.org/lin/similarity/similarity.htm website.
Simply put it, if you want to "mix" (e.g., dissolve) several
components , simply increase their similarity. If you want to
separate them (e.g., by recrystallization), decrease their
similarity.
To reply the second question: good crystals after recrystallization
(same or most similar components get together) gives sharp
MP and higher MP because better crystal is more stable.
-- Dr. Shu-Kun Lin Molecular Diversity Preservation International (MDPI) Saengergasse 25, CH-4054 Basel, Switzerland Tel. +41 79 322 3379, Fax +41 61 302 8918 E-mail: lin$##$mdpi.org http://www.mdpi.org/lin/* Why after cooling (after heating) a solution that contains an organic = (or non organic) compound with a specific solvent, this compound is = recrystallised ?
*How does it happen that the melting point of a compound is a way to = find its purity ?
*Why does polar solvents dissolve polar molecules, while nonpolar = solvents dissolve non polar molecules. __________________
ORGLIST - Organic Chemistry Mailing List Website and Archive: http://www.orglist.net/ List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
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