DEWAR VESSEL (J. Dewar, shotl. the chemist, 1842 — 1923) — the vessel with double walls (between to-rymi is created vacuum) intended for preservation for a long time of the easily evaporating liquefied gases and for cases when good heat insulation of substance is necessary. Of page use also for long-term storage fast-frozen (at t ° — 195 °) cultures of fabrics, plasma and bodies (see. Conservation of bodies and fabrics ). In life apply just arranged glass D. of the page known under the name a thermos, to maintenance of constancy of temperature of foodstuff.
Of page happen generally cylindrical and spherical shape to a roundish bottom, various capacity. Pages make small D. of high-strength glass (fig., and and b); the vessels of bigger volume applied to transportation and storage of liquefied gases — from metal (fig., c).
D.'s heat exchange by the village can happen to the environment at the expense of three factors: convections, radiations and heat conductivity along walls. The heat transfer due to convection almost completely is eliminated with creation of a high vacuum between double walls (10 - 3 — 10 - 5 mm of mercury.); decrease in a heat transfer due to radiation is reached by a covering of internal walls of D. of page silver or copper or their polish.
Modern D. pages provide additional cooling with liquid nitrogen or a liquid air that provides a possibility of long-term storage of various liquefied gases.
Bibliography: Voskresensky P. I. Technology of laboratory works, M., 1973.
Yu. A. Zhukov.