The thermal dissociation of cyanogen into cyanide radicals around 1200deg;C has been studied. Determining the variation of CN concentration with temperature by the intensity of absorption bands, the heat of dissociation 77plusmn;4 kg cal. has been obtained. With this quantity the heat of dissociation of hydrogen cyanide into hydrogen atoms and cyanide radicals is calculated as 94.5plusmn;4 kg cal. By the use of existing thermochemical data these quantities are shown to be the most probable values for the energies of the Csngbnd;C and Csngbnd;H bonds, respectively. The heat of sublimation of carbon is calculated as 154plusmn;3 kg cal.
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