Boiling point and infrared spectroscopy

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Hannahhhhajka
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Is boiling point measurement and infrared spectroscopy effective to assess if the liquid is pure and would these methods be reliable ?
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Flors
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I think so. With infrared spectroscopy you can use one of those mass spectrum graphs( I think they're called!) and find where on the graph it drops so which groups the compound belongs to. Also every compound will have it's own unique fingerprint region that you can also use.

Boiling point is also important though. If you know what the liquid should be you can boil to what it should be. If it evaporates at a lower temperature then you know that it is not pure. It might mean the liquid is more branched, weaker Van der Waals etc which would make the boiling point lower.

I think I might be talking about melting point apparatus but I think the same theory applies for boiling point? I think infrared would be way more reliable than boiling point. If you do boiling point it leaves room for error whereas with infrared it can go through a computer, and make the spectrum graph itself which is more reliable.
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charco
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(Original post by Flors)
I think so. With infrared spectroscopy you can use one of those mass spectrum graphs( I think they're called!) and find where on the graph it drops so which groups the compound belongs to. Also every compound will have it's own unique fingerprint region that you can also use.

Boiling point is also important though. If you know what the liquid should be you can boil to what it should be. If it evaporates at a lower temperature then you know that it is not pure. It might mean the liquid is more branched, weaker Van der Waals etc which would make the boiling point lower.

I think I might be talking about melting point apparatus but I think the same theory applies for boiling point? I think infrared would be way more reliable than boiling point. If you do boiling point it leaves room for error whereas with infrared it can go through a computer, and make the spectrum graph itself which is more reliable.
Another problem with b.p. is that it is subject to the ambient pressure. Unless you have a table of boiling points at different pressures, you have a problem.

More importantly, small amounts of impurities will not change the boiling point by more than the instrumental error.
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