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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: FAN7OM on October 09, 2016, 01:38:03 PM

Title: Lower than expected boiling point?
Post by: FAN7OM on October 09, 2016, 01:38:03 PM

In my lab we performed a distillation and my mixture boiled at 50 degrees celsius. The lab mentioned that the unknown organic solvent (either acetone or isopropanol) is mixed with salt water. Using gas chromatography, my retention time matched that of acetones retention time.

This is frustrating because the chromatography points towards acetone being the unknown, however the lowered boiling point of the mixture contradicts this (acetone boils at 56).

Any ideas would be greatly appreciated.

Title: Re: Lower than expected boiling point?
Post by: AWK on October 09, 2016, 04:20:34 PM

Incorrect mounting of thermometer.

Title: Re: Lower than expected boiling point?
Post by: FAN7OM on October 09, 2016, 04:29:43 PM

lol I actually did not think of that, it sounds about right though.

Thanks!

Title: Re: Lower than expected boiling point?
Post by: Enthalpy on October 13, 2016, 05:11:23 PM

The odour should tell, unless something else stings more.

Title: Re: Lower than expected boiling point?
Post by: Babcock_Hall on October 13, 2016, 06:07:04 PM

Do you have a drawing of the apparatus?  Students often place the thermometer incorrectly, in my experience.

Title: Re: Lower than expected boiling point?
Post by: jasongnome on October 14, 2016, 01:52:44 AM

I think AWK and Babcock Hall have hit the nail on the head.

The thermometer should be positioned at the junction of the condenser.