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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: glaizy on July 04, 2011, 12:52:35 PM

Title: Melting point determination
Post by: glaizy on July 04, 2011, 12:52:35 PM
Why should you always use a new capillary tube with a sample of your compound
when doing a second melting point determination? 

i have searched a lot about this in the internet but i ended up nothing...

 ???
Title: Re: Melting point determination
Post by: discodermolide on July 04, 2011, 01:02:29 PM
Why should you always use a new capillary tube with a sample of your compound
when doing a second melting point determination? 

i have searched a lot about this in the internet but i ended up nothing...

 ???

Because you may have generated a new crystal modification, which has a different MPt.
Or the compound may have decomposed.
Capillary tubes are not expensive
Title: Re: Melting point determination
Post by: glaizy on July 04, 2011, 01:08:59 PM
Why should you always use a new capillary tube with a sample of your compound
when doing a second melting point determination?  

i have searched a lot about this in the internet but i ended up nothing...

 ???

Because you may have generated a new crystal modification, which has a different MPt.
Or the compound may have decomposed.
Capillary tubes are not expensive



THANK YOU SO MUCH!i have some other question regarding melting points..

which has a wider melting range , a mixture or a pure substance?
Title: Re: Melting point determination
Post by: discodermolide on July 04, 2011, 01:21:53 PM
Why should you always use a new capillary tube with a sample of your compound
when doing a second melting point determination?  

i have searched a lot about this in the internet but i ended up nothing...

 ???

Because you may have generated a new crystal modification, which has a different MPt.
Or the compound may have decomposed.
Capillary tubes are not expensive



THANK YOU SO MUCH!i have some other question regarding melting points..

which has a wider melting range , a mixture or a pure substance?

A mixture
Title: Re: Melting point determination
Post by: glaizy on July 04, 2011, 01:49:32 PM
Why should you always use a new capillary tube with a sample of your compound
when doing a second melting point determination?  

i have searched a lot about this in the internet but i ended up nothing...

 ???

what is the effect of the impurity of the boiling point of a substance?

some of my sources said that i will increase and some told me that it will decrease...

 ???

Because you may have generated a new crystal modification, which has a different MPt.
Or the compound may have decomposed.
Capillary tubes are not expensive



THANK YOU SO MUCH!i have some other question regarding melting points..

which has a wider melting range , a mixture or a pure substance?

A mixture