The aim of this experiment is to enable us to understand and carry on the synthesis of acetylsalicylic acid, understand the accomplishments of recrystallisation and the technique of runing point finding. The chief processs are readying of acetylsalicylic acid, recrystallisation of acetylsalicylic acid and in conclusion finding the runing point of the acetylsalicylic acid. For readying of Aspirin, acetic anhydride is added to the mensural sum of salicylic acid. Sulphuric acid is added and heated for a short period to finish reaction. Water is added one time removed from heat with add-on of cold H2O and suction filtration is carried out. As for recrystallisation of acetylsalicylic acid, collected rough merchandise prepared in readying of acetylsalicylic acid which is impure is dissolved in ethyl alcohol and hot distilled H2O is added to the solution. The ticker glass together with the filter paper was weighed and the weighed filter paper was used to transport out the suction filtration. Furthermore, the crystals were topographic points on the ticker glass after drying and its weight was calculated. Then, find the runing point of acetylsalicylic acid utilizing necessary setup. The per centum output was approximately 76.7 % whereas the temperature scope is between 134.2 to 136.1 ISISC. The consequences are within the expected scope and I would reason our experiment was a success.

Felic Hoffman who is a German chemical science formed aspirin in 1897 by looking into Gallic Chemistry Charles Gergardt ‘s experiment and rediscovered the acetylsalicylic acid and produced stable province of acetylsalicylic acid ( The Great Idea Finder 2006 ) . Salicylic acid was extracted from parts of willow trees ( Dermaxime 2011 ) .

Aspirin is a derivative of salicylic acid that is a mild agent that reduces hurting by alleviating concern and musculus and joint achings ( History of aspirin 2011 ) . Aspirin is besides used to handle mild to chair hurting from conditions such as musculus achings, odontalgias and concerns. Aspirin works in our organic structure by barricading certain natural substances in your organic structure to cut down hurting and puffiness ( Aspirin 2011 ) . Esterification is a chemical reaction that is used to do esters in which the Carboxylic acid combines with an intoxicant to organize an ester [ CH3COOC2H5 ] in the presence of a accelerator which is normally concentrated sulfuric acid. It is reversible reaction and they produce sweet smelling merchandises. Esters are widely used in aroma and spirit industry ( Esterification reaction 2010 ) . Aspirin has to be recrystallised several times to obtain pureness. The belongingss that allow this to take topographic point is its bulky chemical group, solubility in H2O and its strong intermolecular forces between the acetylsalicylic acid molecules that allows it to do up the solid substance.


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Aspirin can be used in assorted medical utilizations such as alleviating mild achings and strivings. It can besides be used for a small complex intervention such as bar of blood coagulums and prevent bosom onslaught and shot ( Aspirin and Heart onslaughts 2005 ) . However, there are side effects such as internal hemorrhage to the tummy and other internal variety meats and besides cause people to see asthma onslaughts and unwanted puffinesss ( Vitamin Diary, Aspirin 2010 ) .


Esterification Chemical reaction

Figure 1: Esterification Reaction ( Preparation of Aspirin 1996 )

Shown in figure 1, is the esterification procedure. To organize acetylsalicylic acid, Salicylic acid is reacted with acetic anhydride utilizing sulfuric acid as a accelerator to bring forth Aspirin and Acetic acid. Sulphuric acid is used in this experiment as a accelerator to increase the rate of the reaction without being consumed in the procedure.

Ethanoic Anhydride

There are three grounds why ethanoic anhydride is used instead than other reagents such as ethanoyl chloride even thou they yield aspirin. The grounds are, ethanoic anhydride is cheaper to be purchased compared to ethanoyl chloride. It is besides safer to utilize as it is less caustic and does non readily hydrolyze in H2O unlike the other reagent. Furthermore, it does non bring forth unsafe exhausts of H chloride like ethanoyl chloride ( Chemguide 2004 ) .


Preparation of Aspirin

First, about, 2.4g of salicylic acid was weighed into a dry 100ml conelike flask and recorded. 6ml of acetic anhydride is added into the flask incorporating the salicylic acid in the fumehood. Then, 3-4 beads of concentrated sulfuric acid is added to the mixture and swirled. The mixture was besides heated in the H2O bath for 10 to 15 proceedingss for the completing of reactions. After taking the flask from the H2O bath, 1ml of distilled H2O is added utilizing a dropper to break up the extra acetic anhydride nowadays in the solution. 40ml of cold H2O is added and is stirred and rub utilizing a stirring rod to bring on crystallization. After suction filtration is carried out the rough merchandise is so collected.

Re-crystallization of Aspirin

An approximative 30ml of hot H2O is added to the solution and the rough merchandise is dissolved in a 100ml conelike flask with about 5ml of ethyl alcohol added to it and warmed on a hot home base. As there is solid dividing out, the solution will be warmed till it is wholly dissolved in the solution and was so allowed to chill. Then, a clean, dry ticker glass with 2 filter documents was weighed and recorded. During the suction filtration of the solution, the recrystallised merchandise is collected to the filter paper and was transferred to the ticker glass. This was so put into the oven at 100oC for 15 – 20 proceedingss. Crystals together with the filter paper and the ticker glass was so placed into desiccator for 5 to 10 proceedingss for all the liquid nowadays to be drained. The dried crystals together with the filter documents and ticker glass was weighed and recorded. The weight of dried, recrystallised acetylsalicylic acid is so calculated. The expected output of acetylsalicylic acid was calculated from the sum of acetylsalicylic acid used and the per centum output of the dried, recrystallised acetylsalicylic acid was calculated.

Melting point finding of acetylsalicylic acid

The acetylsalicylic acid was packed into the little capillary tubings and set into the optimelt runing setup to find the liquescent temperature of Aspirin.



Mass of salicylic acid weighed ( a ) = 2.40g

Mass of filter paper & A ; ticker glass ( B ) = 32.96g

Mass of dried, recrystallised acetylsalicylic acid, filter paper & A ; ticker glass ( degree Celsius ) = 34.41g

Mass of dried, recrystallised acetylsalicylic acid ( vitamin D ) is calculated by taking the mass of dried, recrystallised acetylsalicylic acid, filter paper and ticker glass ( degree Celsius ) which is 34.41g and deduct away the mass of filter paper and ticker glass ( B ) which is 32.96g.

( vitamin D ) = ( degree Celsius ) – ( B )

= 34.41g – 32.96g

= 1.45g

Therefore the mass of dried, recrystallised acetylsalicylic acid is 1.45g.

Percent Output

To obtain the percent output of acetylsalicylic acid, we have to happen the moles of salicylic acid used foremost by taking the mass of the salicylic acid which is 2.40g and split by the Mister of salicylic acid.

Number of moles of salicylic acid used ( vitamin E ) = mass/mr

= 2.40/138

= 0.017391 mol

( mol wt of salicylic acid = 138 )

Therefore the expected figure of moles of acetylsalicylic acid ( degree Fahrenheit ) = 0.017391 mol

To cipher the expected mass of acetylsalicylic acid, we have to take the expected moles ( degree Fahrenheit ) which is 0.017391 mol multiply by the Mister of aspirin 180.

Expected mass of acetylsalicylic acid ( g ) = 0.01739 ten 180 = 3.1302 g

( mol wt = 180 )

Then the per centum output can be calculated by taking the mass of dried recrystallised acetylsalicylic acid ( vitamin D ) which is 1.45g and split by the expected mass of aspirin 3.1302g multiply by 100 % .

Percent output = ( vitamin D ) / ( g ) A- 100 %

= 46.3 %

4.3 Melting Point

Temperature scope = 134.2 ISC to 136.1 ISC

4.4 Appearance

White, thin, flakey crystals formed.


My Consequences

Harmonizing to my experiment and the consequences, one conclude that my end merchandise is non truly pure. This can be seen from the computation made based on my experiment utilizing this expression,

Percent output = ( mass of dried recrystallised acetylsalicylic acid / expected mass of acetylsalicylic acid ) x 100 %

Percent output is the sum of substance we have obtained in entire in the experiment. The experimental output per centum is different from the theoretical per centum is because there is loss of merchandise frequently happening during the isolation and purification stairss ( The Synthesis of Aspirin 2010 ) . The percent output of the acetylsalicylic acid obtained from the experiment is 46.3 % output. The higher the output per centum, the higher the pureness of the acetylsalicylic acid will be. Therefore, harmonizing to the consequences, the acetylsalicylic acid obtained is comparatively impure. However, the low per centum output can besides intend that the reactant has non reacted wholly or the reaction is non complete. However there is besides another possibility for the lower per centum output value. It is the add-on of H2O when transporting out suction filtration. As we have to rinse down the crystals before we carry out the suction filtration, some crystals might hold dissolved. Hence, the sum of H2O we use to rinse down the crystals during suction filtration might hold affected the per centum output excessively.

The acetylsalicylic acid crystals are packed into the little capillary tubings and do certain they are all compressed without air spreads. Then they are placed into the thaw setup. The thaw temperature scope of acetylsalicylic acid harmonizing to my experiment is between 134.2 ISC to 136.1 ISC. The theoretical thaw temperature is 140 ISC. Since the scope is near the theoretical value, this shows that the acetylsalicylic acid obtained is quite pure and hence contained fewer drosss.

From both the computations, I can measure that the acetylsalicylic acid is comparatively pure to a nevertheless due to some experimental mistakes or improper techniques practiced, the per centum output is non up to outlook and moreover the incompletion of reaction might besides be one of the grounds to the consequences obtained in this experiment.

Experimental mistakes

There were some experimental mistakes that have caused fluctuation in my consequences compared to the theoretical solutions.

First, after the obtaining the rough merchandise from the first suction filtration, we had to reassign it to the conelike flask to transport out recrystallisation. During this procedure, there were some crystals that got blown off by the air current and some crystals poured on the desk excessively. Hence this might hold affected the per centum output excessively.

Therefore, I had learnt that all wind beginning must be switched off and be kept off from when transporting out this procedure to guarantee truth in consequences.

Second, one time we have dissolved and during the 2nd unit of ammunition suction filtration in effort to obtain the pure acetylsalicylic acid, we forgot to utilize 2 filter documents but alternatively use merely one filter paper on the Buchner funnel. Hence, due to the force per unit area, the filter paper torus and our rough merchandise entered the filter flask that was incorporating the drosss and other liquid. Therefore we had to suction filter the whole mixture in the filter flask and hence, this might hold led to presence of more drosss or lose in merchandise. This might hold affected the consequences.

Figure 2: Apparatus of suction filtration ( Chemistry 104: Synthesis of Aspirin 2010 )

Therefore, from this experiment I learn that I must be more watchful and careful when I carry out suction filtration to avoid unneeded fuss and inaccuracy of consequences and computation.


From this experiment, I have learnt how to transport out suction filtration in the right manner and to be cautious at all clip when managing chemicals and so on. The major experimental findings are that, truth and heed is really of import in this experiment to obtain acetylsalicylic acid that is pure. However, there will be some environmental effects that will still impact the experiment to a little extent.

Finally the aim of the experiment is met and the consequences were acceptable as it is rather accurate.


To better on truth of consequences, we have to take into concern environmental factors such as the fan in the lab. It could impact the experimental findings as it blows off bantam light weight crystals while reassigning them from one topographic point to another. This would take to loss of recrystallised crystals and cause fluctuation in our computations.

When transporting out the suction filtration, it is strongly advisable to utilize 2 or more filter documents to forestall the lacrimation of the filter documents during the suction filtration due to the force per unit area. This would take to the crystals to be in contact with tonss of H2O and do the crystals to fade out. This might besides do inaccuracy to consequences. Furthermore, when reassigning the crystals into the Buchner flask before suction filtration, cold H2O is the most suited to rinse down the crystals as it minimises fade outing of crystals unlike fresh new dissolvers.

All the chemicals must be grips in the fumehood to forestall any caustic chemicals such as salicylic acid, acetic anhydride and sulfuric acid to be in contact with our organic structure. This is so as these chemicals can do annoyance to organic structure parts such as eyes and tegument and can besides do bad Burnss.


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