Page 31 - Practical DF2 Corrected (2)

Pharm D Clinical Pharmacy program 2024-2025 Level 2, Semester 2 Pharmaceutical Dosage Forms II (PT 405)

5) Alkalis:
- These consist of sodium and/or potassium hydroxides, which cause the
saponification of the stearic acid.
- It is better to use a hydroxide than a carbonate, because when stearic acid
is added to a carbonate, it will not set free the carbon dioxide which
would remain in the finished cream.
- The cream would then have numerous minute bubbles rising to the
surface that would sink to the bottom of the jar.

6) Triethanolamine:
- This is a derivative of ammonia.
- It is supplied commercially as mono-, di- and triethanolamines.
- It is a viscous, colourless or faintly yellow liquid.
- It combines with fatty acids to form soap.
- It is soluble in water, alcohol and chloroform.

The formula for preparation of vanishing cream is the following:

Rx/

Purified water 79 g

Stearic acid 15 g

Glycerol 5g

Potassium hydroxide ?g

Perfume and preservative Q.S.

Fiat cream. Mitte 20 g

Knowing that:

- Molecular weight of stearic acid (CH3(CH2)15CH2COOH) = 284.5 g/mol

- Molecular weight of sodium hydroxide (KOH) = 56.11 g/mol

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