Determination of Acid Value | Acid Value in Wax and Fat

This testing method determine of acid values in oil, wax, fat, and acidity test procedure and solvents acid values is KOH used per milligram. 

APPARATUS

a). Heating Mantles.

b). Erlenmeyer Flask 250ml.

c). Burette (Class A).

d). Volumetric Pipette 25 ml (Class-A).

e). Dispensing device.

f). Analytical balance.

REAGENTS & SOLUTIONS

a). Methanolic KOH 0.1N.

b). Neutralized ethanol (95%)

c). Phenolphthalein.

Procedure

a). Weigh 1-2 gm of oil or fat into a 250ml conical or round bottom flask.

b). Add 25 ml of 95% neutralized ethanol.

c). Now heat the content to boiling & shake the flask thoroughly, in order to dissolve the free acid as completely as possible.

d). The solution is cooled & titrated against 0.1 N methanolic KOH and 2-3 drop of an indicator is to be added Under constant shaking. Further, do Vigorous shaking till the pink colour disappears.

e). Heating makes the soap soluble so that titration may be done completely.

f). Endpoint is supposed to be reached when the pink colour persists for 30 secs. In the hot solution after vigorous shaking.

Calculation of Acid Value 

Acid value of oil formula (mg/KOH) = ml of 0.1N KOH  X Factor (F)

                                                    Wt. of sample

Where 

‘F’ = Normality of KOH Solution X equivalent wt. of KOH (56.1gms)

Precautions for Acid Value Testing

a). For higher fatty acid content use 1.0 gm. of sample for better result.

b). For good results always keep the solution hot even if no precipitation occurs. (Oils containing many fatty Acids when titrated with alkali give soaps that precipitate on cooling) and the test sample quantity should not vary much with the quantity of the control sample.

c). The heating time should be the same for the control and test sample.

d). Reagents should be accurately standardized. 

DETERMINE ACIDITY/ACID VALUE IN SOLVENTS AND MONOMERS.

REAGENT

a). Sodium Hydroxide 0.1N solution./ Potassium Hydroxide (0.1N) solution

b). Phenolphthalein indicator.

c). Distilled water.

d). Isopropanol (IPA).

PROCEDURE FOR ACIDITY/ACID VALUE

a). Take 50ml Isopropanol in a 250ml conical flask.

b). Add 2-3 drops of Phenolphthalein indicator. Neutralise the Isopropanol with 0.1N NaOH / 0.1N KOH till it shows light pink colour.

c). Weight 50gms. Of the sample into the above flask and shake well. Titrate it with the 0.1N NaOH /

 0.1N KOH solution, till slight pink colour, persists.

Acidity / Acid value, mg KOH/g = B.R.x N x 56.11

                                               Sample was taken gms

% Acidity as CH3COOH = B.R.x N x 60.05

                                         Sample taken gms x 10

Where,

B.R. = Volume of NaOH / KOH (0.1N) solution.

N = Normality of NaOH/KOH

>Determine Of Neutralization Value........