Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: jena on February 02, 2005, 05:22:10 PM

Title: Melting Points
Post by: jena on February 02, 2005, 05:22:10 PM

Hi

I don't really understand the principle behind melting points? Why is necessary to know the melting points of an item?

Thank You  :)

Title: Re:Melting Points
Post by: Mitch on February 02, 2005, 05:45:23 PM

They are used as a measure of purity.

Title: Re:Melting Points
Post by: Donaldson Tan on February 02, 2005, 07:10:03 PM

if melting/freezing a substance is among the steps you take in a chemical process, you gotta know the melting point in order to make an estimate for the required energy input for the entire process. it's not only an economical issue but also knowing if your equipment can tolerate the heat output and pressure changes throughout the process.

Title: Re:Melting Points
Post by: dexangeles on February 03, 2005, 12:26:35 AM

example1: you need to record the melting point of a salt substance and you decide to use a melt-temp....if you don't know the melting point is probably over 400 degrees, and you decide to use the melt-temp at #2 (slow heat) setting, you'll be there all day  ;)

example2: helps isolate a desired substance (just like distillation - gota know the Bp and keep it there to isolate the desired compound)

example3: it helps provide for finding out what an unkown is (besides ftir, nmr, gc, etc...)  Imagine if we don't have a CRC book for reference of melting points.  Organic is hard enough :'(