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THE SYSTEM Na 2 O‐B 2 O 3 , IV Vapor Pressures of Boric Oxide, Sodium Metaborate, and Sodium Diborate between 1150°C and 1400°C
Author(s) -
Cole Sandford S.,
Taylor Nelson W.
Publication year - 1935
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1935.tb19358.x
Subject(s) - analytical chemistry (journal) , molality , chemistry , vaporization , vapor pressure , sodium , boiling point , aqueous solution , organic chemistry , chromatography
Vapor pressures of B 2 0 3 , Na 2 O, B 2 O 3 , and Na 2 O.2B 3 O were obtained at 50°C intervals between 1150°C and 1400°C, utilizing the dynamic method with dry N 2 under normal atmospheric pressure. Assuming normal vapor densities, the vapor pressures in millimeters of mercury at O°C were as follows:Temperature, °C B 2 O 3 Na 2 O·B 2 O 3 Na 2 O·2B 2 O 31150 2.55 2.1 1200 0.83 7.2 5.5 1250 2.0 28.0 13.0 1300 3.4 62.0 25.5 1350 6.9 160.01400 12.0The calculated boiling point was found to be 1860°C for B 2 O 3 , 1434°C for Na 2 O‐B 2 O 3 , and 1575°C for Na 2 O.2B 2 O 3 . The molal entropy of vaporization of B 2 O 3 was found to be 32.2 calories per degree. The molal heat of vaporization was calculated to be B 2 O 3 , 65,600 cal.; Na Z O.B 2 O 3 , 96,910 cal.; and Na 2 O.2B 2 O 3 , 72,410 cal. B 2 O 3 and Na 2 O.B 2 O 3 volatilized without change in composition, but Na 2 O.2B 2 O 3 was found to dissociate at all temperatures studied. It yielded a vapor of calculated composition 51.6% Na 2 O, 48.4% B 2 O 3 . Vapor pressure data based on this composition are also reported.