During an aspirin purity test using melting point I used pure salicylic acid powder, my crude sample and my acetylcyclic acid that I synthesized. What should be my general trend in melting point? and why? Also what is purpose of the crude sample
Measuring the melting point of a substance is a good way to test for purity. In this
experiment you use the melting point as a way of investigating the purity and identity
of laboratory prepared aspirin samples.
A pure substance usually has a sharp melting point – ie a narrow temperature range
during which it changes from a solid to a liquid. A substance which contains
impurities often melts over a range of several degrees.
Any impurities in the substance cause a lowering and broadening of this characteristic
temperature.
Substance Melting point
2-Hydroxybenzoic acid 158–160 °C
Aspirin 138–140 ° C
