A pure substance usually has a specific melting point – ie a narrow temperature range when it changes from a solid to a liquid

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A pure substance usually has a specific melting point – ie a narrow temperature range when it changes from a solid to a liquid. Any impurities in the substance causes a lowering and broadening of this characteristic temperature.
Aspirin 138–140 ° C
Iron(III) will react with the deprotonated form of salicylic acid (salicylate ion) to form a purple solution (Spectroscopic analysis). This reaction only occurs with these two substances. Hence, this is a method used to determine the amount of free salicylic acid in the sample as the maximum allowed is 0.15% salicylic acid. he me you she too right left too