Harmful Space
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
This article from the 1928–1936 Soviet Great Medical Encyclopedia defines harmful space as the residual volume within air pumps and connecting tubes that prevents the creation of a perfect vacuum. It provides a mathematical relationship to calculate the minimum pressure limit achievable based on the volumes of the harmful space, the evacuated space, and the piston, along with atmospheric pressure.
Encyclopedia entry (1928–1936)
HARMFUL SPACE, the space remaining between the piston of an air pump in its extreme position and the recesses in the cylinder walls, as well as the space inside all kinds of connecting tubes and valves. In the presence of harmful space, an ideal vacuum cannot be created (see). If the volume of the harmful space is denoted by S, the volume of the evacuated space by V, the volume of the piston by Q, and atmospheric pressure by P, it can be shown that the gas pressure cannot be lowered beyond the limit: Pmin = — P.
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“Harmful Space.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.pages.dev/article/harmful-space/