Why is the bore of the capillary tube of a mercury thermometer made narrow?
dh25sThe vapour pressure of mercury (Hg) is low (0.0017 torr at 25 oC). The vapour pressure is dependent on temperature, thus what you want to measure. As the temperature increases, the vapour pressure increases and the mercury imbibes further up the capillary. If the capiallry radius were larger, the readings would be more difficult to see, i.e. the precision would decrease.
