Practical investigations
Read our general notes on Risk Assessment
I'm doing my practical investigation on the amount of aspirin in various brands of aspirin tablets and I was wondering if there is any point checking for the purity of the aspirin by checking the melting point. In order to do this, would I need to separate the aspirin in the tablet from the rest of the impurities? If so, how should I do that?
Igloo writes
In order to check the purity, you could measure the melting point, but you’re correct, you would certainly need to remove the “filler material” first. Since the latter is largely a mixture of insoluble matter such as cellulose, silica and starches you could try grinding the tablets into water, using suction filtration, and then using crystallisation to isolate the “aspirin”. However, I am by no means certain that this would be successful since some of the starch is likely to accompany the aspirin into the filtrate. Also this method assumes that the aspirin and the most likely contaminant – salicylic acid – will both crystallise out together, and this is by no means inevitable, since I suspect that the latter is far more water-soluble.
Perhaps all this is worth trying – unless you can think of anything better – and then mentioning the caveats in your report.
Always carry out a risk assessment and check with your teacher before starting any practical work.
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.
back to Practical investigations
Rate this page or react
Share your views on this page, 0 ratings so far
updated: 14 December 2006
