Practical investigations
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I have finished my advanced higher chemistry project on aspirin. I got an extremely low value for my Rf value of salicylic acid: 0.67, and for my own lab-based aspirin I got 0.85. I can’t think of how to explain this low value? I have re-done the experiment but still got a low result. For my report I have written how the acid may have been contaminated but are there any other factors which may have resulted in me getting such a low value? 260308
Igloo writes ...
Rf values are extremely difficult to measure accurately, since the “spot” is usually relatively large and it is hard to estimate its focal point. I have found that salicylic acid and aspirin have very similar Rf values, using paper chromatography and water as the eluant, and it is possible therefore that your own lab-based sample (which probably contained both) may be showing both “spots” effectively merged together. You could try using a different stationary phase and a different solvent to see if things improve.
Risk assessment
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updated: 28 March 2008
