Milk

Preparation of Standards

Weight of NAOH required to prepare 0.1N 500ml solution  = E*V*N
                                                                                                          1000

Where

           E= equillent weight
           V= required volume
           N=required normality

Equillent weight of NAOH= 40

         Weight of NAOH      = 40*500*0.1  
                                                   1000
                                            = 2gm

Weigh out accurately about 2gm of NAOH pellets dissolved in water and dilute 500ml.

• Standardization of  NAOH

  Preparation of 0.1N standard oxalic acid,

Equilent weight of oxalic acid = 63

Weight of oxalic acid required to prepare 100ml 0.1N =  E*V*N 
                                                                                                 1000 

                                                                                             = 63*100*0.1
                                                                                                    1000
                                                                                             = 0.63

Weigh out accurately about 0.63gm of oxalic acid and dissolving water. Make up the solution 100ml standard volumetric flask.

Normality     = Weight per liter
                        Equilent weight

                    = 0.63*10
                           63
                    = 6.3 
                        63
                    = 0.1

 Pipette out 20ml oxalic acid in to 250ml conical flask add 2-3 dropes of phenolphthalein indicator solution. Titrate against NAOH from a burette end point is appearance of pink color.

V1N1   = V2N2
     N2   =   V1N1
                     V2        

Where

     V1= volume of oxalic acid
     N1= normality of oxalic acid
     V2= volume of NAOH

• PHENOLPHTHALEIN INDICATOR SOLUTION

  Dissolve 1gm of phenolphthalein in 100ml neutral alcohol