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Analysis of Aspirin Tablets.

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Introduction

Analysis of Aspirin Tablets Background Information Aspirin is a well-known drug, which is analgesic and antipyretic. Analgesic drugs are those that relieve pain. Antipyretics are ones that lower body temperature. The main component of aspirin tablets is: 2 - Ethanoylhydroxybenzoic acid CH3COOC6H4COOH After aspirin is swallowed, it is unchanged in the acidic conditions of the stomach, but is hydrolysed by the alkali juices in the intestines. Hydroxybenzoates lower body temperature quickly and very effectively in fever patients, but they have little or no effect if the temperature is normal. They are also analgesics, which relieve pain, such as headaches. The toxic dose from hydroxybonzoates is relatively large; their uncontrolled use could be dangerous. Aspirin, one of the first drugs to come into common usage, is still mostly the widely used in the world - approximately 35,000 metric tonnes are produced and consumed annually, enough to make over 100 billion standard aspirin tablets every year. Aspirin is analgesic, anti-inflammatory, antipyretic and is an inhibitor of platelet aggregation. It inhibits fatty acid cyclo-oxygenase by acetylation of the active site of enzyme and the pharmacological effects of aspirin are due to the inhibition of the formation of cyclo-oxygenase products including prostglandins, thromboxanes and prostacyclin. ...read more.

Middle

* To hydrolyse the aspirin acid - heat it gently for 10 minutes. SAFETY: eye protection must be worn. * Cool the mixture and transfer (with washings) to a 250 cm�-graduated flask. Fill up to the blue mark with distilled water. Part 3 - Estimating the quantity of unused NaOH after hydrolysis * Put 25 cm� of the hydrolysed solution (from part 2) into a conical flask using a pipette. * Put a couple of drops of Phenolphthalein indicator in the solution. It should go purple. * Titrate this against 0.1-mol dm-3 HCl acid (which is in the Burette). * Carry out the titration until the solution goes colourless (keep shaking the beaker whilst releasing the HCl acid). Results Part 1: Titration Rough Accurate 1 Accurate 2 Final reading (cm�) 25.65 25.25 25.30 Initial reading (cm�) 0.00 0.00 0.00 Amount of HCl acid added (t1) 25.65 25.25 25.30 Average (t1) = (25.25 + 25.30) 2 = 25.275 cm� of HCl acid Part 2: Mass of aspirin tablets = 1.66 g Part 3: Titration Rough Accurate 1 Accurate 2 Final reading (cm�) 7.90 15.80 23.65 Initial reading (cm�) 0.00 8.00 16.00 Amount of HCl acid added (t2) ...read more.

Conclusion

Burette: This is accurate to 0.05 cm�. If the reading has to be rounded because the scale on the Burette is not big enough to be exact, this will also cause an error. Graduated Flask: If the volume of the flask is 250 cm�, the bottom of the meniscus is on the calibration line, the error is 0.1 cm�. Pipette: Once again, the scale is not extremely accurate and may cause an error. Procedural errors: It could have been difficult to spot the endpoint of the reaction. Despite the solution being purple, and the colour looked for was colourless - it may be hard to get the exact amount of HCl added to go colourless. This is because the releaser of the Burette may release too much of the HCl acid when you know you only need a small amount of it for the solution to go colourless. The equipment may not have washed well (drying is also very important). Some of the HCl acid may have got onto the side of the conical flask and not reacted with the hydrolysed aspirin. If an acid-base titration had been carried out, it would not have been a good idea to put too much indicator in, because the indicator itself is a weak acid. ...read more.

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