Mercury-in-glass thermometer Mercury-in-glass thermometer The mercury-in-glass or mercury thermometer was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam (1714). It consists of a bulb containing mercury attached to a glass tube of narrow diameter; the volume of mercury in the tube is much less than the volume in the bulb. The volume of mercury changes slightly with temperature; the small change in volume drives the narrow mercury column a relatively long way up the tube. The space above the mercury may be filled with nitrogen gas or it may be at less than atmospheric pressure, a partial vacuum. In order to calibrate
Six's thermometer in the push-button type with the magnetic plate in place, there is a risk of damaging the weak magnet behind the scale, or magnetising the steel in the markers either weakening or enhancing the pulling force against the capillary tube on all or part of the scale so that the thermometer no longer works properly. The original Six's thermometer design contains mercury, which has been banned for most uses in the European Union and some other parts of the world. In 2006, S.Brannan & Sons Ltd, a UK company, was granted a patent for a mercury-free version of Six's maximum–minimum