Keyword: density

The main reasons are non-homogeneity of the oil in storage, thermometer calibration, and other experimental errors.

Heating alone, even though at recommended storage temperatures, may not be enough to ensure a completely homogeneous and representative sample, especially in large storage tanks. This inevitably leads to inaccuracies in density determination.

The use of stirrers or agitators in combination with heating helps to produce a more homogeneous liquid and more uniform temperature readings. Care should be taken never to allow oils to cool below recommended storage temperatures such that heating becomes ineffective in producing a homogeneous liquid.