ISO 1739:1975

Butter — Determination of the refractive index of the fat (Reference method)

Describes a method of measurement which uses a refractometer with a scale graduated in refractive index units to the third decimal place and having prisms heated by means of a circulating liquid at 40 degrees centigrade, the temperature being thermostatically controlled to within +/- 0.1 degrees centigrade. A sodium vapour lamp shall be used as a light source.