Pulse Glass

• Pulse glass functioning principle
• Boiling and condensation

This simple device consists of a narrow tube bent at right angles at either end, with two larger spheres on the ends. The tube is roughly one-third to one-half filled with water or alcohol, evacuated, and sealed. Because of the vacuum, the liquid in the glass can be brought to a boil by holding it in one’s hand. Several toys are now made from pulse glasses, including the ‘fever meter’ and the ‘drinking duck’.

In holding a pulse glass in your hand you can observe some surprising phenomena and experience some curious sensations. As Franklin notes, “the instant it begins to boil a sudden coldness is felt in the ball held.” What Franklin discovered was that the boiling temperature of water depends on the atmospheric pressure. This observation influenced and inspired James Watt to generate power with a steam machine. The pulse glass produced new knowledge and led to many technological innovations and inventions. It gave the scientist and inventor the confidence of being able to produce desired phenomena intentionally and control some physical parameters purposively. The knowledge of these phenomena and their relations enables know how. The observation of phenomena is thus fundamental both for science and technology.

• Pulse glass, balls 40 mm length 130 mm — 4210.50