Aim: Determination the percentage purity of the given sample of a sulpha drug having molecular weight _________.

Requirement:

  • Acetone
  • 10 % sodium acetate
  • Potassium dichromate solution (10%)
  • Standard AgNO3

Process: Weigh exactly about 0.2 gm of the given sample of sulpha drug and dissolve in a mixture of 25 ml Acetone & 20 ml 10 % sodium acetate solution (Warm it if necessary). Add 1 ml K2Cr2O7 solution and titrate it against 0.1 N AgNO3. At the end point yellow color of the solution is replaced by permanent faint red color. Perform the experiment in duplicate / triplicate.

Carry out the blank determination omitting the addition of the sulpha drug.

% purity of sulpha drug = \frac{\left(V_1-V_2\right) \times N \times M \times 100}{W \times 1000}

Where V1  = ml of AgNO3 used for sample

            V2   = ml of AgNO3 used for blank

             N   = Normality of AgNO3 solution

             M   = Molecular weight of sulpha drug

             W   = weight of sample in gm.

Results: % purity of sulpha drug =                     

Observation:

  • Blank Estimation:

Burette     : 0.1N AgNO3 solution

Flask         : 25 ml acetone + 20 ml 10 % CH3COONa + 1 ml K2Cr2O7 solution

End point : Yellow to faint red colour

No. I.B.R. F.B.R. Difference Constant B.R.

V1 ml
01
02
  • Actual Estimation:

Burette    : 0.1N AgNO3 solution

Flask        : 0.2 gm of sulpha drug + 25 ml acetone + 20 ml 10 % CH3COONa + 1 ml K2Cr2O7 solution

End point : Yellow to faint red colour

No. I.B.R. F.B.R. Difference Constant B.R.

V2 ml
01
02

 

Chemical Reaction:

Calculation:

% purity of sulpha drug     =        \frac{\left(V_1-V_2\right) \times N \times M \times 100}{W \times 1000}

Where, V1 = ml of AgNO3 used for sample

             V2 = ml of AgNO3 used for blank

             N = Normality of AgNO3 solution

             M = Molecular weight of sulpha drug

             W = weight of sample in gm.