PREPARATION OF ACETYL SALICYLIC ACID (ASPIRIN)



REQUIREMENTS:

Apparatus:

Beakers, Test tubes, Balance, Spatula, Water bath, Stirrer, Filter paper etc

Chemicals:

Salicylic acid ……………………………………….. 10gm

Acetyl chloride …………………………………….. 7.5gm

Pyridine …………………………………………….. 7.0ml



THEORY:

·         White crystals, commonly needle like or white, crystalline powder; odourless; taste, slightly acid; stable in dry air.

·         Solubility: It is soluble in 300 parts of water, in seven parts of alcohol, in 20 parts of solvent ether, in 17 parts of chloroform and with decomposition in solutions of alkali hydroxide and of alkali carbonates.

·         Melting point: It is about 136o. The substance is being placed in the heating bath at about 130o and the temperature being raised at the rate of 4o to 6o per minute.
PROCEDURE:

1)       I took salicylic acid (10gm) in a beaker and then I dissolved in pyridine (07ml), to get  the clear solution.

2)      Then I added acetyl chloride (7.5gm) portion wise.

3)      I placed the beaker in water bath at 50-60 oC for 30minutes with continuous stirring.

4)      Then the contents were transferred  in 300ml cold water.

5)      I filtered it with the help of filter paper, so that I got clear crystals.

6)      I washed it and dry it by pressing  in filter paper

7)      Then I weighed the dried crystals.


PRECAUTIONS:..

1)      Wash the beakers before solution preparation.

2)      Weigh the ingredient carefully

3)      Prepare clear solution of salicylic acid

4)      Mentain the temperature at 50-60 oC.

5)      Before re-weighing, must dry the crystals.





TO DETERMINE THE MELTING POINT AND PURIFICATION OF CRUDE ASPIRIN BY CRYSTALIZATION

REQUIREMENTS:

Apparatus:                                                                                     

Melting pint apparatus (Gallenkemp), Beakers, capillary tubes, Balance, Spatula, Water bath, Stirrer, Filter paper etc

Chemicals:

Crude aspirin, ethanol



PROCEDURE:

Melting point determination:

8)      I take crude aspirin and inserted some quantity in capillary tube.

9)      Then I placed the capillary tube in the Gallenkemp apparatus.

10)  By this I determined the melting point of crude aspirin.

Crystallization of crude aspirin:

11)  I weighed crude aspirin in a beaker and then added ethanol portion wise so that clear solution of aspirin prepared.

12)  Then I placed it in a water bath for a few  minutes.

13)  When the supersaturated solution obtained, I taken off  the beaker.

14)  Then I filtered the content with the help of filter paper and I placed  it at  room temperature for a few minutes.

15)  I kept the crystals until it become fully dried.

16)  Then I weighed the dried crystals and determined the percent (%) yield.



PRECAUTIONS:

6)      Take three reading of crude aspirin on Gallenkemp apparatus.

7)      Wash the beakers before solution preparation.

8)       Before re-weighing, must dry the crystals



CALCULATIONS AND RESULT




Result of crude aspirin melting point


       Average reading of aspirin melting point =                       


                                        Result of crystallization of crude aspirin        


Weight of the filter paper (A) =
Weight of the filter paper + aspirin crystals (B) =
      Weight of wet aspirin crystals (C) =

                                                             =               
                                                             =                 
       Weight of dry aspirin crystals (D) =          
      Weight of crude aspirin (E) =
By the help of this we can find the %age yield, using the following formula;
                         
                                                             = 



ASSAY OF ASPIRIN POWDER

REQUIREMENTS:

Apparatus:                                                                                     

Beakers, Volumetric flask, Test tubes, Balance, Spatula etc

Chemicals:

Sodium hydroxide (0.5 M), Hydrochloric acid (0.5 M), Ethanol, Phenolphthalin.



PROCEDURE:

1)      I dissolved 0.5gm of aspirin powder  in 10ml of ethanol to form a clear solution.

2)      I added 40ml of 0.5M sodium hydroxide solution in it and it was boiled for 10minutes.

3)      A blank titration was carried out with 0.5M sodium hydroxide solution and 0.5M HCl solution.

4)      The solution was then titrated against 0.5M HCl solution.

5)      The difference between two readings was calculated, which would give volume of sodium hydroxide used to neutralize aspirin.

6)      The difference between  the two reading was calculated and the following factor was then used to calculate the aspirin content.

2ml of 0.5M NaOH = 0.045gm of aspirin



                                                              

CALCULATIONS Table

                                          

Preparation of 0.5M Hydrochloric Solution

                = 4.1 ml per 100ml

Preparation of 0.5M Sodium Hydroxide Solution

                                         01M Sodium hydroxide solution = 40g/1000ml

                                    0.5M Sodium hydroxide solution = 20g per 1000ml

                                    0.5M Sodium hydroxide solution = 20 mg per ml

Preparation of 0.5M Aspirin Solution

01M Aspirin solution = 90g/1000ml

                                    0.5M Aspirin solution = 45g per 1000ml

                                    0.5M Aspirin solution = 45 mg per ml

Determination of Percent Purity

Aspirin + 2NaOH                                                    + CH3COONa + H2O

           180gm         40gm



Volume of 0.5M HCl solution used to neutralize blank 0.5M NaOH =

Volume of 0.5M HCl soln used to neutralize Aspirin solution           =        

Volume of 0.5M NaOH solution used to neutralize Aspirin               =

                                                                                                                         =

1ml of 0.5M NaOH solution neutralize   =                  of Aspirin              

11ml of 0.5M NaOH solution neutralize =

                                                                 =                 of Aspirin

            So;

            

                Percent purity =                    × 100

                                                            

                                       =           purity


Share To:

Social Community

Post A Comment:

0 comments so far,add yours