Emulsifying Wax

Definition

Emulsifying Wax contains Cetostearyl Alcohol and either Sodium Lauryl Sulfate or sodium salts of similar sulfated higher primary aliphatic alcohols.

Extemporaneous preparation

The following formula and directions apply.

Melt the Cetostearyl Alcohol and heat to about 95°. Add the Sodium Lauryl Sulfate, mix, add the Purified Water, heat to 115° and maintain at this temperature, stirring vigorously, until frothing ceases and the product is translucent. Cool quickly.

Characteristics

An almost white or pale yellow, waxy solid or flakes, becoming plastic when warmed.

Practically insoluble in water, forming an emulsion; partly soluble in ethanol (96%).

Identification

Tests

Acidity

To 20 g add a mixture of 40 mL of ether and 75 mL of ethanol (96%) previously neutralised to phenolphthalein solution R1 and warm gently until solution is effected. Titrate with 0.1m sodium hydroxide VS using phenolphthalein solution R1 as indicator until a pink colour which persists for at least 15 seconds is obtained. Not more than 1.0 mL of 0.1m sodium hydroxide VS is required.

Alkalinity

Disperse 5.0 g in 25 mL of warm ethanol (96%) previously neutralised to phenolphthalein solution R1 and cool. No colour is produced on the addition of 0.5 mL of phenolphthalein solution R1.

Alcohols

To 3.5 g of the residue obtained in the test for Unsaponifiable matter add 12 g of stearic anhydride and 10 mL of xylene and heat gently under a reflux condenser for 30 minutes. Cool, add a mixture of 40 mL of pyridine and 4 mL of water, heat under a reflux condenser for a further 30 minutes and titrate the hot solution with 1m sodium hydroxide VS using phenolphthalein solution R1 as indicator. Repeat the operation without the residue. The difference between the titrations is 12.8 to 14.2 mL.

Iodine value

Not more than 3.0 (iodine monochloride method), Appendix X E.

Saponification value

Not more than 2.0, Appendix X G. Use 20 g.

Sodium alkyl sulfates

Not less than 8.7%, calculated as C₁₂H₂₅O₄SNa with reference to the anhydrous substance, when determined by the following method. Dissolve 0.25 g as completely as possible in 15 mL of chloroform, add 30 mL of water, 10 mL of 1m sulfuric acid and 1 mL of dimethyl yellow and oracet blue 2R solution and titrate with 0.004m benzethonium chloride VS, shaking vigorously and allowing the layers to separate after each addition, until the chloroform layer acquires a permanent clear green colour. Each mL of 0.004m benzethonium chloride VS is equivalent to 1.154 mg of C₁₂H₂₅O₄SNa.

Sulfated ash

1.8 to 3.3%, Appendix IX A.

Unsaponifiable matter

Not less than 86.0%, calculated with reference to the anhydrous substance, Appendix X H. Use 5 g and omit the titration of the residue.

Water

Not more than 4.0% w/w, Appendix IX C. Use 0.6 g.