General methods on determination of cosmetics
—Determination of relative density
1 Scope
This part of GB/T 13531 specifies the test methods for relative density of liquid and semi-solid cosmetics.
Methods I and II in this part are applicable to the determination of relative density of liquid cosmetics.
Method III in this part is applicable to the determination of relative density of liquid and semi-solid cosmetics.
2 Method I: Density bottle method
2.1 Principle
The relative density of cosmetic sample and distilled water is equal to the mass ratio of sample to distilled water of the same volume measured at a certain temperature.
2.2 Apparatus
2.2.1 Density bottle: 25 mL, having thermometer with a division value of 0.5°C.
2.2.2 Thermostatic waterbath: temperature control accuracy ± 0.5°C.
2.2.3 Analytical balance: with a sensibility of 0.0001 g.
2.3 Procedures
Take a clean density bottle, put it in a drying oven at 100°C ~ 105°C to dry to constant weight, and weigh its mass (accurate to 0.0001 g). Fill the density bottle with distilled water which has just been boiled and cooled to about 2°C lower than the specified temperature. Insert a thermometer, and then place the bottle in a thermostatic waterbath at the specified temperature for 20 min. After the distilled water reaches the specified temperature, wipe off the water overflowing from the capillary with filter paper, and cover with the cap. Take the density bottle out of the waterbath, wipe off the water on the bottle, and weigh its mass (accurate to 0.0001 g).
Carefully add the sample into a clean and dry density bottle, insert a thermometer, and weigh its mass using the thermostatic waterbath method used for weighing distilled water.
Foreword i
1 Scope
2 Method I: Density bottle method
3 Method II: Hydrometer method
4 Method III: Instrument method
