Total Active Ingredients for Sulfated Oils or Fatty matter

This method determines the total active ingredients as they exist in the original. and total Active ingredients for sulfated oils. Applicable to sulfonated or sulfated oils. Free alkali or alkali bound as soap is not included. Unsulfaded and unsulfonated oil and unsaponifiable fatty matter are included. 

In the case of sulfated oils only, the total active ingredients may be estimated by calculation since it is equivalent to the sum of the desulphated fatty matter and neutralized organically combined sulfuric anhydride.


1. Ethyl ether (LR grade )

2. Sodium chloride ( AR grade ) 

3. Sodium Sulfate, Anhydrous

4. Methyl orange indicator

5. Alcoholic KOH Solution. 0.5 N ( Accurately standardized )


Weight 5 to 10 gm. of the sample, depending upon the concentration of the fatty matter, into a 250 ml separatory funnel containing 50 ml. of saturated NaCl solution, a few gm. of solid NaCl, 2 to 3 drops of methyl indictor, and 50 ml of ether.

Shake the mixture and neutralize with 1.0N H2SO4 until the lower layer is distinctly pink. Highly sulfated oils at this stage may form three layers instead of two. In such cases use a fat solvent consisting of two parts of ether and one of 95% alcohol, instead of ether only.

Allow the mixture in the separatory funnel to settle for at least 5 min. draw off the lower layer into another separatory funnel and continue washing the ether layer with 25 ml portions of NaCl solution until 1 drop of 0.5N NaOH turns the wash water strongly alkaline when methyl orange indicator is used.

Allow all separations to settle for at least 5 min. Combine the water layers and extract with two 25 ml portions of ether. Combine the last 2 ether extracts and wash with NaCl solution until free from acid, as in the case of the ether layer in the first funnel. Combine all the ether layers in the 300 ml. Erlenmeyer flask.

Carefully remove any water that may settle and dehydrate the ether layer as follows: add 5 gm of anhydrous sodium sulfate and shake vigorously for 5.0 min. and filter directly into a 150 ml beaker or flask, placed in a water bath.

Wash the flask and filter with ethyl ether until free from fat and add the filtrate to beaker. To prevent the oil from creeping, the volume in the beaker or flash should at no time during the filtration and washing exceed 50 ml.

Evaporate the ether solution until the volume has reduced to 20 ml and transfer the residue to a crucible. In this case, the beaker must be previously dried and cooled in a desiccator to room temp. and weighed.

Evaporate to a volume of 20 ml and then add exactly 2.0 ml of alcoholic potassium hydroxide solution. Mix by swirling and then evaporate until free from the ether. 

Note:- With highly sulfonated or sulfated oils, it may be necessary to add 5-10ml of the alcoholic KOH solution in the Oder to stabilize the residue.

Dry in an air oven at 105± 2 °C for 30 min. Cool in a desiccator to room temp. and weigh. Repeat drying for 30-minute periods until constant weight is obtained.

Total Active ingredients for sulfated oils

Active ingredients Calculation 

(a) Total active ingredients %= ( Weight of residue - alkali correction) *100
                                                            Weight of sample

Alkali correction = 0.0006789*(ml of KOH*N)

N = Normality of KOH

0.0006789 = molecule's ratio of (K---H) : KOH divided by 1000

(b) For Sulfated Oils Only:

Total active ingredients (by calculation) %= P+1.4871*Y

1.4871 = molecular ratio of NaSO4: SO4

P =% total desulphated fatty matter.

Y = % combined SO3.  

Total Anhydrous Soap | Determination of total fatty matter in soaps


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