Aim: Determination of saponification value of given an oil sample

Principle: Saponification value defines as the number of mg of KOH required to saponify or hydrolysis 1 g of oil/fat. In this estimation KOH reacts with the fat/oil to gives glycerol and the potassium salt of the corresponding fatty acid. KOH is added in excess and the amount remaining after saponification is estimated by titrating with standard acid.

Saponification value is an index of mean molecular of the fatty acids of glyceride comprising a fat. Lower the saponification value higher the molecular mass.

Procedure: weight accurately between 1.0 to 2.0 g of the given oil/fat into a round bottom flask. Add 25 ml of 0.5 M alcoholic KOH and then add 10 ml alcohol heat the flasks under the reflux for 30 min. simultaneously carry out blank which out the sample at the end  titrate the remaining KOH in each flask with 0.5 M HCl using phenolphthalein as indicator.

Standardization of KOH:  Weight accurately the given amount of KHP (Potassium hydrogen thelate) in weighing bottle and transfer the whole amount in to 150 ml. conical flask and dissolved KHP in 25 ml. distilled water and titrate with KOH using Phenolphthalein indicator and note the volume of KOH .

Result:

The saponification value of given oil sample is = _______

Calculation:

Standardization of KOH

(1)        Weight of KHP = 0.500 g

(2)        Indicator = Phenolphthalein

(3)        Color change = colorless to pink

(4)        Volume of NaOH used as V1 = __________

Normality of KOH = \frac{Weight of KHP\times 1000}{204.2\times V1}

Determination of saponification of oil/fat

  • Weight of oil/fat taken = ___________
  • Reading of test solution (T) = __________
  • Reading of blank solution (B) = __________

Ester value = \frac{(B - T)\times N\times 56}{W}

T = ml of HCl required to neutralize unused alcoholic KOH

B = ml of HCl during blank titration

N= normality of KOH solution

W= weight of an oil sample