Melting point

  • #1
I have a sample of 25 % acetanilide with 75 % caffeine.


I record a melting point range of 198 - 240 degrees celcius



acetanilide's melting point is 114.3
caffeine's melting point is 238

What would cause this huge experimental range?

My thinking is that the acetanilide is covered in caffeine, and finally melts, at a higher temperature. Im not really sure about this, please help!
 

Answers and Replies

  • #2
Astronuc
Staff Emeritus
Science Advisor
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How do you define melting?

In mixed systems, particularly metal alloys, there is often a liquid and solid phases, and the solid and liquid phases may have different compositions.

Is the composition constant? In other words, were you measuring one mixture with that composition? How many measurements did you make? If multiple measurements, did you allow for cooling in between?

Perhaps there is a dissolution of caffeine into the acetanilide.
 

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