The mercury vacuum pump, also known as the Gaede pump, is a type of vacuum pump that was a significant innovation in the development of vacuum technology. Invented by the German physicist Wolfgang Gaede in 1905, the Gaede mercury pump represented a major breakthrough in the ability to create high vacuums in laboratories and industrial applications.

The operating principle of the Gaede pump relies on the use of mercury as a medium to seal and create a vacuum. The pump functions through a mechanism that evaporates mercury, with the vapor then condensed in a cooler part of the system. This process removes air or gas molecules from the space being evacuated, creating a vacuum. A distinctive feature of the Gaede pump is its use of a rotary system that improves the efficiency of gas removal, enabling the achievement of higher vacuum levels than was possible with earlier technologies.

The invention of the mercury vacuum pump by Gaede was crucial to the advancement of various fields of science and technology, including experimental physics, chemistry, and the manufacturing of electric lamps and vacuum tubes. Furthermore, this technology paved the way for the development of more advanced and efficient vacuum pumps, such as diffusion pumps and turbomolecular pumps, which can achieve even deeper vacuums without the need for mercury, a toxic and hazardous material.

Despite its historical significance, the use of mercury pumps has declined due to the environmental risks and toxicity of mercury, being replaced by safer and more effective methods of creating vacuums.