Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Excipient.
DEFINITION
Wax obtained by bleaching yellow beeswax.
CHARACTERS
Appearance
White or yellowish-white pieces or plates, translucent when thin, with a fine-grained, matt and non-crystalline fracture; when warmed in the hand they become soft and malleable.
It has an odour similar to that of yellow beeswax, though fainter and never rancid. It is tasteless and does not stick to the teeth.
Solubility
Practically insoluble in water, partially soluble in hot ethanol (90 per cent V/V) and completely soluble in fatty and essential oils.
Relative density
About 0.960.
TESTS
Drop point (2.2.17)
61 °C to 66 °C.
Melt the beeswax by heating on a water-bath, pour onto a glass plate and allow to cool to a semi-solid mass. Fill the metal cup by inserting the wider end into the beeswax and repeating the procedure until beeswax extrudes from the narrow opening. Remove the excess with a spatula and insert the thermometer immediately.
Remove the beeswax displaced.
Allow to stand at room temperature for at least 12 h before determining the drop point.
Acid value
17.0 to 24.0.
To 2.00 g (m g), in a 250 mL conical flask fitted with a reflux condenser, add 40 mL of xylene R and a few glass beads. Heat until the substance is dissolved. Add 20 mL of ethanol (96 per cent) R and 0.5 mL of phenolphthalein solution R1 and titrate the hot solution with 0.5 M alcoholic potassium hydroxide until a red colour persists for at least 10 s (n1 mL). Carry out a blank test (n2 mL).
Acid value = 28.05(n1−n2)
Ester value (2.5.2)
70 to 80.
Saponification value
87 to 104.
To 2.00 g (m g), in a 250 mL conical flask fitted with a reflux condenser, add 30 mL of a mixture of equal volumes of ethanol (96 per cent) R and xylene R and a few glass beads. Heat until the substance is dissolved. Add 25.0 mL of 0.5 M alcoholic potassium hydroxide and heat under a reflux condenser for 3 h. Titrate the hot solution immediately with 0.5 M hydrochloric acid, using 1 mL of phenolphthalein solution R1 as indicator (n1 mL). Reheat the solution to boiling several times during the course of the titration. Carry out a blank test (n2 mL).
Saponification value = 28.05(n2−n1)
Ceresin, paraffins and certain other waxes
To 3.0 g, in a 100 mL round-bottomed flask, add 30 mL of a 40 g/L solution of potassium hydroxide R in aldehyde-free alcohol R and boil gently under a reflux condenser for 2 h. Remove the condenser and immediately insert a thermometer. Place the flask in a water-bath at 80 °C and allow to cool, swirling the solution continuously. No precipitate is formed until 65 °C, although the solution may be slightly opalescent. Beginning at 65 °C, the solution may become cloudy and precipitates may be formed. At 59 °C, the solution is cloudy.
Glycerol and other polyols
Maximum 0.5 per cent m/m, calculated as glycerol.
To 0.20 g add 10 mL of alcoholic potassium hydroxide solution R and heat on a water-bath under a reflux condenser for 30 min. Add 50 mL of dilute sulfuric acid R, cool and filter. Rinse the flask and the filter with dilute sulfuric acid R. Combine the filtrate and washings and dilute to 100.0 mL with dilute sulfuric acid R. Place 1.0 mL of the solution in a test-tube, add 0.5 mL of a 10.7 g/L solution of sodium periodate R, mix and allow to stand for 5 min. Add 1.0 mL of decolorised fuchsin solution R and mix. Any precipitate disappears. Place the tube in a beaker containing water at 40 °C. During cooling observe for 10-15 min. Any violet-blue colour in the solution is not more intense than that in a standard prepared at the same time and in the same manner using 1.0 mL of a 10 mg/L solution of glycerol R in dilute sulfuric acid R.
