What does it mean if the percent purity of a synthesized aspirin is 100% and the commercial is 90%?

Question

What have I done wrong

Answer 1

Hello, thank you for taking the time to post your question!

I wouldn’t think of these values as indicating something that you have done “wrong” … basically it’s saying that the synthesized version has 100% purity, meaning that there is nothing else in there … it’s perfectly pure aspirin. Then the commercial being at 90% means that 10% of the aspirin is some other substance.

I hope that helps get you moving in the right direction! Feel free to reach out if you have any additional questions beyond that :)

Answer 2

Bobby,

That's an odd question -- do you mean that you synthesized the aspirin and tested it to be 100% pure, or what? You've just stated two facts; unless you propose a hypothesis of why that might be so, there's nothing to be wrong about, yet! That being said, IF the stated assay values can be trusted, your commercial aspirin has undergone considerable decomposition (usually it's quite close to 100% pure when first made and tabletted). [You might wish to reference the US Pharmacopoeia for current purity requirements for aspirin tablets.] It would smell heavily of vinegar (acetic acid), and you should dispose of it, as with all surplus/expired chemicals, in an environmentally acceptable way -- which in the case of aspirin, could be adding to the mulch bucket for your garden (salicylic acid is common enough in nature).

Of course, if your chemistry course is still giving you a headache, maybe that's something you might use your new sample of commercial aspirin for ....? Just kidding!

-- S. de Riel