With a properly constructed ice bath, it is possible to create a temperature reference standard of 0.0C0.02C. We can then use this ice bath to verify the calibration of our secondary standard, a glass thermometer. This is done by immersing the glass thermometer in the ice bath and taking a reading. If, for example, the glass thermometer read 0.10C, then the glass thermometer is out by 0.10C. This is the correction factor for the thermometer. Every reading taken with this thermometer would be high by this amount; therefore we would subtract 0.10C to get the cor¬rected temperature.