GB/T 13531.7-2018 English PDF (GBT13531.7-2018)

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GB/T 13531.7-2018: General methods on determination of cosmetics -- Determination of refractive index
GB/T 13531.7-2018
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.70
Y 42
General Methods on Determination of
Cosmetics – Determination of Refractive Index
ISSUED ON. FEBRUARY 06, 2018
IMPLEMENTED ON. SEPTEMBER 01, 2018
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Terms and Definitions ... 4
3 The First Method. Abbe Refractometer Method ... 4
4 The Second Method. Automatic Refractometer Method ... 6
General Methods on Determination of
Cosmetics – Determination of Refractive Index
1 Scope
This Part of GB/T 13531 specifies the determination of refractive index for the liquid
and semi-solid cosmetics.
The first method of this Part is applicable to the determination of refractive index for
the transparent liquid cosmetics.
The second method of this Part is applicable to the determination of refractive index
for the liquid or semi-solid cosmetics.
2 Terms and Definitions
The following terms and definitions are applicable to this document.
2.1 Refractive index
The ratio between the sine of the incident angle and the sine of the refraction angle,
when the light with certain wavelength is incident from the air into a sample, which
maintain at a constant temperature.
NOTE. The wavelength is specified to be (589.3±0.3)nm, which corresponds to the Lines D1
and D2 in the sodium spectrum.
3 The First Method. Abbe Refractometer Method
3.1 Principle
The Abbe refractometer measures the refractive index of a sample is based on the
principle of determining the critical angle as per the law of refraction. Directly measure
the refraction angle or observe the critical line of total reflection; the tested sample
shall maintain the state of isotropic and transparent.
3.2 Reagents
3.2.1 Unless otherwise is specified, the used reagents shall be analytically pure; the
standard.
3.4.3 Determination procedures
3.4.3.1 Clean the surface of the prism before the determination; use the absorbent
cotton to pick up the volatile solvents of ethanol and ether; then wipe the solvents; the
prism is completely dry.
3.4.3.2 Connect the constant temperature water bath with the prism; adjust the water
bath temperature; so that the prism temperature is maintained at the desired operating
temperature.
3.4.3.3 Calibrate the refractometer reading as specified in 3.4.2. Repeat the
operations in 3.4.3.1 and 3.4.3.2.
3.4.3.4 Add a few drops of sample to the lower prism with a dropper; quickly close
the prism and tighten. The sample shall be evenly filled with the view field without
bubbles. Standard for a few minutes till the prism temperature restores to the desired
operating temperature.
3.4.3.5 Align the light source, observe with eyepiece; rotate the compensator spiral
to make the boundary between the light and dark clear; and the color disappears
completely. Then rotate the scale pointer spiral; so that the diving line just passes the
focus of the “╳” line on the objective lens.
3.4.3.6 Accurately read the refractive index on the scale to the four digits after
decimal point.
3.5 Result expression
The measurement results shall be expressed by the average of two measurements;
the result shall be retained for three digits after the decimal point.
3.6 Precision
The absolute error of two parallel tests is no greater than 0.002.
4 The Second Method. Automatic Refractometer
Method
4.1 Principle
The refractive index of sample measured by the automatic refractometer is based on
the determination of the critical angle of the total reflection.