The oil in the oil filled bimetallic thermometer white is what causes?

Oil filled bimetallic thermometer is a round shape into threaded heat bimetallic strip as thermal devices, and put it in a protective sleeve tube, one end is fixed, known as the fixed end, the other end connection on a thin shaft, a free end. Spool at the free end is equipped with a pointer. When the temperature changes, the resulting thermal devices the free end of the rotation, drive the thin axis from the Angle of the pointer changes, corresponding temperature indicator on the dial. So the cause of oil charge double metal temperature of plan hair white what? Make the oil in the oil filled double metal thermometer whitish may be the following two main reasons: 1. Manufacturers use glycerin is too cheap, impurity is in the oil; 2. Oil filled the use circumstance temperature of the thermometer, undermining the oil internal composition, causing the oil physical properties change and the metamorphic pale.