Synthesis of aspirin why filter with cold water

In case of contact, rinse with plenty of water. Ask instructor to assist with the cleaning of any spills. Acetic anhydride is a lachrymator its vapor irritates the eyes causing tears to flow.

Keep it in the fume hood. Waste Disposal:. The reaction mixtures used in this experiment may be safely disposed of in the sink, followed by copious amount of running water.

Solids, aspirin and salicylic acid, should be disposed of in the regular trash container. Section 3: Procedure. Part 1: Synthesis of Aspirin. Prepare a boiling-water bath by filling a mL beaker with about mL of tap water. Put the beaker on the hot plate. Weigh out about 2. To do this, first tare a piece of weighing paper This means to put a piece of paper on the balance and press the zero or tare button.

It is OK to weigh a little extra mass do not return excess salicylic acid to its container as this might contaminate the entire amount if your spatula is not perfectly clean. Record the mass of the solid. Place this solid into a mL Erlenmeyer flask other sizes may be acceptable. In the fume hood , measure out 4 mL of acetic anhydride in a small graduated cylinder and add it to the flask. From this point on, keep your flask under the hood, because it now contains acetic anhydride the vapors of acetic anhydride are very irritating.

Add about 5 drops of concentrated sulfuric acid. This will be the catalyst for the reaction. Place the flask in the boiling water bath and clamp it in place. Heat the reaction for at least 15 minutes. Put at least 60 mL of laboratory water into a mL beaker or similar size. Then put this beaker in an ice-water bath.

Use this cold water in steps 9, 12, 13, and 14 below. After the reaction has heated for at least 15 minutes, remove it from the boiling water bath. In 1 or 2 mL portions, add about 10mL cold water to the reaction, swirl the reaction between each mL portions. This water will react and destroy any remaining acetic anhydride. Put the flask with the reaction into an ice water bath Fig. Crystals of aspirin should form. Chill for at least 10 minutes in order to obtain the maximum amount of crystalline product.

Collect the aspirin crystals by vacuum filtration. 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. Air dry the crystals and transfer them to a watch glass to dry. Test a small amount of the product for the presence of unreacted salicylic acid using the ferric chloride solution.

When the product is completely dry, weigh the product, determine its melting point lit mp oC and calculate the percentage yield. Dissolve the final product in a minimum amount no more than mL of hot ethyl acetate in a 25 mL Erlenmeyer flask. Make sure that the product is completely dissolved while gently and continuously heating on a steam bath. Cool the solution to room temperature and then in a ice-bath. Collect the product by vacuum filtration and rinse out of the flask with a few milliliters of cold petroleum ether.

When the product is completely dry, weigh its weight, determine its melting point lit mp. Submit the crystalline sample in a small vial with proper labeling to your instructor. Do this test with 1. It effectively diminishes the pain of problems such as headaches, toothaches and joint pains. It works by reducing substances in the body that cause fever, pain and inflammation.

Cold water is used instead of warm water to reduce the amount of dissolving the product. Using an ice bath slows down the molecules, enabling them crystallize. The aspirin is characterized by melting point at the end. To check whether the product is pure, the melting point range should be minimal. Procedure Synthesis of the aspirin: 1. The actual weight is recorded. In the fumehood,5mL of acetic anhydride is added to salicylic acid in the flask.

An ester and water will be formed. To this mixture,drops of concentrated sulfuric acid is added and the mixture is swirled. This will speed up the reaction. If necessary, the solution is warmed. Do not let it boil. Recrystallization is performed to purify the aspirin which is usually done by dissolving the substance in a suitable solvent , which is hot. Approximately 30mL of hot distilled water is added into the solution on a hotplate one the solid dissolves. The solution is cooled to room temperature and then it is placed in an ice-bath in the fumehood for approximately mins.

The solution is not to be agitated while cooling. Using an ice bath slows down the molecules in the solution, enabling them crystallize. A clean, dry watch glass with two pieces of filter papers are weighed and recorded. Why does the aspirin need to be cooled down?

And why do we wash the aspirin with chilled water? Improve this question. Add a comment. Active Oldest Votes. Improve this answer.

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