Purity determinations by differential thermal analysis.
Measurement of the melting-point depression of impure samples was compared with a differential method that involved running the impure sample against a pure sample of the same material. Samples of highly purified benzophenone to which had been added known quantities of 4-methylbenzophenone were studied. The area under the curve was proportional to the difference in purity between the sample and reference material over the range studied, 0.3-2.0 mole % with a standard deviation of 0.10 mole %, an uncertainty only half as large as one obtained by the melting-point depression method with the same apparatus.
Bowman
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Department of Chemistry, Purdue University, Lafayette, Indiana 47907, U.S.A.
Roger S
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