Uncovering the Mystery of Acetanilide and Caffeine Melting Point Range

[pitchharmonics]

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. I am not really sure about this, please help!

 

[Astronuc]

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.

 

[ravenprp]

There are a few factors that could contribute to the large experimental range you have observed in your sample of 25% acetanilide and 75% caffeine. One possibility is that the two substances have different melting points and may not mix evenly, leading to varying melting points throughout the sample. Another factor could be impurities in either the acetanilide or caffeine, which can affect the melting point and result in a wider range. Additionally, the heating rate and technique used during the melting point determination can also impact the observed range. It is important to carefully control these factors in order to obtain a more accurate and consistent melting point range. Further experimentation and analysis may be needed to determine the exact cause of the observed range in your sample.