up to which temperature the mercury thermometer is used for measure
Mercury-in-glass thermometer Mercury thermometers cover a wide temperature range from −37 to 356 °C (−35 to 673 °F); the instrument's upper temperature range may be extended though the introduction of an inert gas such as nitrogen. This introduction of an inert gas increases the pressure on the liquid mercury and therefore its boiling point is increased, this in combination with replacing the Pyrex glass with fused quartz allows the upper temperature range to be extended to 800 °C (1,470 °F).