Rosin Acid Percent by Mass of TFM | Rosin Dimer Fatty Acid

Determination of ROSIN ACID % BY MASS OF TFM (IN BAR SOAPS)

APPARATUS

1. Conical Flask-250ml, of chemical resistant glass with a standard taper 24/40 neck.

2. Condenser -Water-cooled with joint fitting the flask given in step1.

3. Separatory funnel-500ml, Pear-shape, fitted with a glass stopper.

4. Burette-50ml capacity with 0.1ml divisions.

REAGENTS 

1. Methanol-99.5 percent.

2. Sulphuric Acid-Relative Density 1.84

3. Dissolve 100g of anhydrous sodium sulfate (Na2SO4) in water.

4. Ethyl Ehter-Reagent Grade.

5. Methyl Orange Indicator- Dissolve 0.1g of Methyl Orange in 100ml of water.

6. Ethyl Alcohol-Neutral 95Percent Ethyl Alcohol, or neutral denatured Alcohol.

7. Phenolphthalein Indicator-Dissolve 1g of Phenolphthalein in 100ml of methanol.

8. Standard Alcoholic Potassium Hydroxide Solution (0.2N or 0.5N)-Dissolve 13.3g of Potassium Hydroxide (Preferably in Pallet form) for a 0.2N solution or 3.3 g for 0.5 N solution in methanol Dilute to 1 liter with methanol. Standardize to ±0.001N. The standardized solution should be protected against evaporation and absorption of carbon dioxide from the air and should be standardized frequently.

PROCEDURE 

Dissolve 40 ± 0.1g of the sample in 100 ml of methanol in a 250 ml conical flask. Swirl the flask to dissolve the oil and add a clean boiling chip.

Add slowly 5ml of sulphuric acid while swirling the flask vigorously. Connect the flask to the condenser, apply heat, and reflux the contents for 10 minutes. Cool the flask to room temperature with cold water. Add 250ml of sodium sulfate to a 500ml separatory

funnel. Pour the contents of the flask into the funnel and complete the quantitative transfer of the contents of the flask with 100ml of ether.

Thoroughly shake the mixture in the funnel. Allow to settle, draw off the salt layer and discard. 

Wash the contents of the funnel twice again with 250ml portions of sodium sulfate solution. The last washing should not react pink to the methyl orange indicator. 

After removing the last wash, drain the contents of the separatory funnel into a 500 ml conical flask. Rinse the funnel with 20ml of ether and add the rinsings to the flask.

Add 20 ml of ethyl alcohol and 1ml of phenolphthalein indicator. 

Titrate to the appearance of a pink-red color using 0.2N alcoholic potassium hydroxide solution if the rosin acid content is less than 5 percent and 0.5N if more than 5 percent.

CALCULATION 

Calculate the percentage of rosin acids as follows:

                                                    1.031 × V × N × 30.2

ROSIN ACIDS, PERCENT BY MASS = --------- - 

                                                           0.74 M

Where

V= Volume in ml of standard potassium hydroxide solution used in the titration.

N= Normality of Potassium Hydroxide solution used,

M= Mass in g of the sample taken for analysis, and 0.7