Measurement of Enthalpies of Evaporation of Bi and Bi2by an Optical Absorption Technique

摘要

The enthalpies of evaporation of Bi and Bi2were determined by the secondhyphen;law method using an optical absorption technique to measure the change of vapor density with temperature for each species. The 3067hyphen;Aring; line was used for Bi and the band head at 2731 Aring; was used for Bi2. The enthalpy of dissociation of Bi2is the difference between the two enthalpies of evaporation. The evaporation values obtained werethinsp;thinsp;Bilpar;lrpar;equals;Bilpar;grpar;Dgr;Hcompfn;298equals;49thinsp;600plusmn;1100thinsp;cal,thinsp;thinsp;Bilpar;lrpar;equals;12Bi2lpar;grpar;Dgr;Hcompfn;298equals;24thinsp;700plusmn;1000thinsp;cal,12Bi2lpar;grpar;equals;Bilpar;grpar;Dgr;Hcompfn;298equals;24thinsp;900plusmn;2100thinsp;cal.The optical absorption technique was checked on lead, using the 2833hyphen;Aring; line. For lead, the Dgr;Hdeg;v,298measured was 47 240plusmn;850 cal, as compared with an accepted value of 46 600plusmn;300 cal.