Practical investigations
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Hi, I am going to use colorimetry with iron(III) to determine impurities in asprin. I know that I must make a calibration curve with different concentrations of salicylic acid, however I do not know what is a good starting concentration. Is 0.01 too high or too low?! I cannot find starting data anywhere, only procedures! Thanks!
Corrie writes ....
Ideally the concentration range of your calibration curve should cover the expected concentration range of the salicyclic acid impurity in the aspirin solution you are making up to use in the colorimeter.
The maximum (but unlikely) concentration of salicylic acid would be the same as the aspirin concentration, i.e. 100% impurity! At the other end of the scale, if you assume the impurity is not less than 1% of the aspirin, that gives you the minimum concentration of salicylic acid to use for your calibration curve.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
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updated: 16 March 2007
