Final answer:
Mercury is used to measure blood pressure because it is more dense than other liquids.
Step-by-step explanation:
Mercury is used to measure blood pressure because it is more dense compared to other liquids. The density of mercury is 13.6 times greater than water, making it a suitable choice for measuring high pressures, such as those found in the arterial blood vessels. In comparison, using water to measure blood pressure would require a manometer more than 30 feet tall, which is impractical.
The density of the liquid used in a manometer affects the height of the liquid column and mercury's higher density allows for a more compact and manageable column. Therefore the use of mercury as a measuring liquid is preferred over other liquids due to its density and practicality in accurately measuring blood pressure.