| 释义 |
Dewar, dewar|ˈdjuːə(r)|
The name of Sir James Dewar (1842-1923), British physicist and chemist, used attrib. or absol. to designate a double-walled vessel or flask, usu. of glass or copper, having the space between the walls empty of air to prevent conduction and convection of heat to and from the inner container. Cf. vacuum-bottle, -flask, and -vessel s.v. vacuum 4.
1899T. O'C. Sloane Liquid Air xi. 246 The Dewar vacuum bulb consists of a double or treble walled glass vessel, with the space or spaces between the vessels hermetically sealed and with a nearly perfect vacuum therein. Ibid. 248 Various shapes and modifications of Dewar bulbs. 1902Encycl. Brit. XXX. 281/2 Vacuum or ‘Dewar’ vessels. 1930Engineering 5 Sept. 314/1 A calorimeter consisting of a wide-necked Dewar flask, [etc.]. 1964N. G. Clark Mod. Org. Chem. vii. 112 The reaction is carried out in a Dewar vessel. 1966New Scientist 21 July 138/3 A replenisher that automatically maintains the level of liquefied gas in a dewar has been developed.
Add:b. Chem. Used attrib. with reference to a possible structure (proposed by Dewar) for the benzene molecule in which one bond forms a bridge across the benzene ring; Dewar benzene, the isomer of benzene having a Dewar structure.
1913J. B. Cohen Org. Chem. Adv. Students II. v. 387 That the parallel double linkage of the Dewar formula is responsible for luminescence..is seen in certain hydropyridine carboxylic esters. 1949G. W. Wheland Adv. Org. Chem. (ed. 2) x. 420 Approximate calculations have..led to the conclusion that the Dewar structures are of only small (although still far from insignificant) importance in the resonance. 1962Van Tamelen & Pappas in Jrnl. Amer. Chem. Soc. LXXXIV. 3790/1 In this contribution we describe a hydrocarbon the properties of which lead us to propose that it is the first isolated member of the ‘Dewar benzene’ class. 1979Jrnl. Org. Chem. USSR XV. 1401 (heading) Calculation of the reaction paths for 1,3-sigmatropic shifts of the C–S bond in allyl hydrosulfide and Dewar thiophene. 1987Jrnl. Amer. Chem. Soc. CIX. 7888/1 The high aromatization temperature required for a short-bridged Dewar benzene has precedent. |