The Newton linseed oil thermometer: an evaluation of its departure from linearity

This paper considers the bias of the Newton linseed oil thermometer with respect to the non-linearity of thermometric liquid expansion. The bias is larger than for mercury thermometers but much smaller (5 times less) than for alcohol thermometers. The bias of linseed oil thermometers increases with temperature, and the maximum is achieved in summer; in the UK it may underestimate the temperature by as much as -0.5 degC relative to mercury thermometers. The evaluation of the bias has been possible thanks to some calibration experiments performed in the eighteenth and nineteenth century.