ISO 6320:2017 pdf download

ISO 6320:2017 pdf download.Animal and vegetable fats and oils — Determination of refractive index
1 Scope
This document specifies a method for the determination of the refractive index of animal and vegetable fats and oils.
Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this document.
2 Normative reference
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 661, Animal and vegetable fats and oils — Preparation of test sample
ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definition
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1 refractive index (of a medium)
ratio of the velocity of light of a definite wavelength in a vacuum to its velocity in the medium
Note 1 to entry: In practice, the velocity of light in air is used in place of that in a vacuum and, unless otherwise specified, the selected wavelength is the mean wavelength of the sodium D lines (589,6 nm).
Note 2 to entry: The refractive index of a given substance varies with the wavelength of the incident light and with temperature. The notation used is n t
D, where t is the temperature in degrees Celsius.
4 Principle
By means of a suitable refractometer, the refractive index of a liquid sample is measured at a specified temperature.
Maintain the temperature of the prism of the refractometer at the required constant value by circulating through the instrument water from the water bath (6.4). Monitor the temperature of the water issuing from the refractometer using a suitable precision thermometer. Immediately before the measurement, lower the movable part of the prism to a horizontal position. Wipe the surface of the prism with a soft cloth and then with a piece of cotton wool moistened with a few drops of the solvent (5.2). Allow to dry. Carry out the measurement according to the operating instructions for the instrument being used. Read the refractive index to the nearest 0,000 1 as an absolute value and record the temperature of the prism of the instrument. Immediately after the measurement, wipe the surface of the prism with a soft cloth and then with a piece of cotton wool moistened with a few drops of the solvent (5.2). Allow to dry. Measure the refractive index twice more, calculate the arithmetic mean of the three measurements and take this as the test result.