Practical investigations
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I am currently doing an investigation on the purity of aspirin. I have found that the melting point of aspirin is about 135 °C. However, when I crushed a SOLUBLE aspirin tablet to test the melting point the sample did not melt even at 200 °C. Can you tell me whether soluble aspirin has a different melting point and why it does not melt at 135 °C?
Igloo replies
Aspirin is a covalent compound and an acid, whereas “soluble aspirin” is the sodium salt of aspirin, and is therefore ionic. The relatively strong ionic forces in a soluble aspirin tablet cause its melting point to be much higher than that for aspirin itself.
Risk assessment
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updated: 18 January 2006
