What is the acid value of oleic acid?

Answer 1

Determination of Acide value

By Colouv indication titration

Total Acide Number ( mg.KoH/g.)

Reagent:-

1- Ethanol 95% (v/v) ( Standard)

2-Alcohol KOH 0.1N ( Standard)

3-HCL 0.1N ( Standard)

4- Ph . ph in Ethyl alcohol 0.5%

5- Alkali blue solution

6- Toluene

Procedure No.(1): -

1-weight about 10 gm. Sample in conical flask 250ml. ( in case of oil have low PH take a large amount of sample )

2-in another beaker put a mixture of (60ml. Toluene +40ml. Ethanol 95% + 2ml. Alkali blue solution)

3- Neutralize a mixture with KOH Solution until Red Rosecolor appear ( End point)

4-Add a Neutralize mixture on sample with steering until purple bluecolor appear

After a complete solubility of sample occur (Mixture-2)

5- Neutralize a Mixture-2 with Alcohol KOH 0.1N ( Standard) until color change from faint blue to Red Rose ( End point) stable for 15 sec.

*The last method is the best in case of OIL with dark color and high viscosity over 120 cent stook.

-Procedure No.(2):

1-weight about 10 gm. Sample in conical flask 250ml.

2- in another beaker put a mixture of (1ml. Ph . ph +50ml. Ethanol 95% and heat for ( 40 : 50 C )

3-Neutralize a mixture with Alcohol KOH 0.1N ( Standard) Solution until faint Red color appear ( End point)

4- Add Ethanol 95% (v/v) ( Standard) on sample and enter to Air Condenser and heat until boiling in water bath and leave a mixture for 5 min. with shaking in cycler motion to ensure acid extraction

5- Add 1ml. of Ph . ph in Ethyl alcohol 0.5% and cool to 40 : 50 C and Neutralize a mixture festally with Alcohol KOH0.1N ( Standard) Solution until faint Red color appear ( End point)

* The 2nd. method is the best in case of OIL with faint color and low viscosity.

Calculation:

56.1 X N X V

A = -------------------------- Where A= Total Acide Number ( mg.KoH/g.)

V= Alcohol KOH 0.1N(Volume) W

Per (g) Sample weight= w

(Alcohol KOH 0.1N ( Standard N=(Normality) of

References: Elementary practical organic chemistry3rd. Edition Arthur 1. Vogel

Quantitative organic Analysis

Answer 2

It is reported to be between 8.0-8.5. This is also a research article indicating that the pKa is 9.85.

Answer 3

The acid value of oleic acid is approximately 198-207 mg KOH/g. Acid value measures the amount of acidic compounds present in a chemical substance, with higher values indicating higher acidity.