Why is asa washed with cold water

Cool the mixture slightly in an ice bath until crystallization is completed. The product will appear as a solid mass when crystallization is completed. Add 50 mL of water and cool the mixture in an ice bath. Do not add the water until crystal formation is complete. Vacuum filter the product using a Buchner funnel. You can use some of the filtrate to rinse the Erlenmeyer flask if necessary.

Rinse the crystals several times with small portions 5 mL of cold water and air dry the crystals on a Buchner funnel by suction until the crystals appear to be free of solvent. Test this crude product for the presence of unreacted salicylic acid using the ferric chloride test. Record the weight of the crude solid which probably contains water.

Stir the crude solid with 25 mL of a saturated aqueous sodium bicarbonate solution in a 15O mL beaker until all signs of reaction have ceased evolution of CO 2 ceases. Filter the solution through a Buchner funnel to remove any insoluble impurities or polymers that may have been formed.

Wash the beaker and the funnel with 5 to 1O mL of water. Carefully pour the filtrate with stirring, a small amount at a time, into an ice cold HCl solution ca 3. Make sure that the resulting solution is acidic blue litmus paper and that the aspirin has completely precipitated out.

Filter the solid by suction and wash the crystals 3X with 5 mL of cold water each. Remove all the liquid from the crystals by pressing with a clean stopper or cork. Note: It is best to add the acid slowly with stirring to mix the contents rather than just pouring the acid into the beacker. Stirring and adding slowly should prevent sodium salicylate from becoming entrapped in the solid salicylic acid. You may need to add more than 25 mL of 3 M sulfuric acid for example, you will need more than 20 mL just to neutralize the NaOH used in the reaction.

Solid salicylic acid should form as the neutralization proceeds. After pHydroin paper shows a pH of 1, add mL more of the 3 M sulfuric acid to ensure all the salicylic acid precipitates.

The mixture will be acidic, but too much acid will not be a problem: Acid stays acid in acid! Cool the mixture in an ice-water bath to about 0 o C. Let beaker stay in the ice bucket for about 15 min while allowing the crystals to settle. The salicylic acid must must be a slurry before you do the filtration.

So, if the solid is not freely flowing in the beaker, add enough water so that the solid is suspended and a liquid slurry appearance.

Carefully wash the beaker with ice cold water, if necessary, to transfer all the crystals to the funnel. Store the salicylic acid crystals in an evaporating dish or beaker in the drying oven until the next lab period.

Since your collected crystals from an acid solution, you cannot store your filter paper with your chemical. Aspirin is a trade name for acetylsalicylic acid, a common analgesic. Acetylsalicylic acid is an acetic acid ester derivative of salicylic acid.

The earliest known uses of the drug can be traced back to the Greek physician Hippocrates in the fifth century B. He used powder extracted from the bark of willows to treat pain and reduce fever. Salicin, the parent of the salicylate drug family, was successfully isolated in from willow bark. Sodium salicylate, a predecessor to aspirin, was developed along with salicylic acid in as a pain reliever.

Sodium salicylate was not often popular though, as it has a habit of irritating the stomach. However, in , a man named Felix Hoffman changed the face of medicine forever. Hoffman was a German chemist working for Bayer. He had been using the common pain reliever of the time, sodium salicylate, to treat his father's arthritis.

The sodium salicylate caused his father the same stomach trouble it caused other people, so Felix decided to try and concoct a less acidic formula. His work led to the synthesis of acetylsalicylic acid, or ASA. This soon became the pain killer of choice for physicians around the globe. Scientists never really understood the inner workings of the drug however. It wasn't until the 's, when British pharmacologist John Vane, Ph.

Vane and his colleagues found that aspirin inhibited the release of a hormone like substance called prostaglandin. This chemical regulates certain body functions, such as blood vessel elasticity and changing the functions of blood platelets.

Thus can aspirin affect blood clotting and ease inflammation. The reaction for synthesis of acetylsalicylic acid is shown in the following figure. Salicylic acid, prepared from the hydrolysis of methylsalicylate is reacted with acetic anhydride producing the ester product, acetylsalicylic acid. In a previous experiment, we have used the Fischer esterification reaction to produce isopentyl acetate from an acid acetic acid and an alcohol isopentyl alcohol.

The current experiment uses the carboxylic acid derivative, acetic anhydride, for ester formation. The advantage of using acetic anhydride is that you do not produce water which can be used for hydrolysis of the newly formed ester. Concentrated sulfuric acid will be used to keep everything in the protonated state. Acetic anhydride is the preferred acid derivative to synthesize aspirin commercially because the acetic acid produced in this reaction a reaction by-product can be used again, by converting it back into acetic anhydride.

If you recovered less than 3. However, if you recovered at least 3. Initiate the aspirin synthesis reaction: Preheat mL of water in a mL beaker to boiling. Place about 3. This addition of acid allows the carbonyl carbon of acetic anhydride to be more electrophilic. Heat the flask containing your reactants by placing it into a beaker of boiling water for five or six minutes. Stir the mixture by gently swirling the flask.

During this time, the solid should dissolve completely. Isolation of aspirin Remove the flask from the boiling water bath, and add 15 mL of ice water to it. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why is crystalline aspirin washed with chilled water in the purification process? Ask Question. Asked 7 years, 5 months ago. Active 7 years ago. Viewed 29k times. Why does the aspirin need to be cooled down?

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