The vapour pressure thermometer consists of thermal bulb 1, capillary tube 2 and bellows 3, housed in airtight box 7. When the temperature and, consequently, the pressure increase in the vapour pressure thermometer, the force acting on the bellows box also increases, the bellows and spring 5 are compressed, stem 4 of the valve moves downward and closes the valve to some extent, reducing the supply of heat-carrying agent to the system. When the pressure in the system is reduced, spring 5 raises box 7, stretching the bellows. As a result, the clear opening of the regulating valve increases. The regulator is set to the required tempherature by changing the initial compression of the spring. This is done by adjusting washer 8 to the corresponding graduation of scale 9. Pressure gauge 6 with a temperature scale serves to check the temperature.
$4098$EHP,Rg$