Celsius thermometer and importance of mercury in making thermometers
The Celsius thermometer
The Celsius thermometer is the thermometer that is used to measure the temperature of liquids , the Swedish scientist ” Andres Celsius ” created the Celsius scale 1747 , While recording the temperature , the thermometer must be vertical and the direction of sight must be perpendicular to the thermometer .
Andres Celsius considered the zero as the melting point of ice and 100 degree Celsius as the boiling point of water , He divided the distance between zero and 100 degree Celsius into 100 parts , where each part equals one degree .
The Celsius thermometer consists of transparent thick glass tube , a capillary tube closed from one of its ends , and mercury bulb that filled with mercury and connected to the other end of the capillary tube .
There is no constriction above the mercury bulb in the Celsius thermometer , the thermometer scale starts from zero degree Celsius to 100 degree Celsius , and every degree is represented by one part on this scale .
There are some types of Celsius thermometers whose scales reach 200 degree Celsius , In Celsius thermometer , the lower fixed point is 0 degree Celsius which known as the melting point of ice or the freezing point of water , and the upper fixed point is 100 degree Celsius which known as the boiling point of water .
Some thermometers contain two scales , one represents Celsius scale and the other represents Fahrenheit scale , where 0 degree Celsius = 32 degree Fahrenheit and 100 degree Celsius = 212 degree Fahrenheit .
Why mercury is preferred in making thermometers ?
Mercury is a regular expanding material ( expands regularly ) , that makes mercury gives an accurate estimation , and it does not stick to the walls of the capillary tube .