Molecular Association in Sodium Cyanide Vapor

Mass spectra of vapors from samples of NaCN indicate that the compound evaporates as NaCN(g) and Na2(CN)2(g) molecules at temperature around 1000°K. The mass spectrum resembles that obtained for sodium halide and hydroxide vapors. A comparison of relative ion currents produced by electron bombardment of NaCN vapors effusing from single- and double-oven-type Knudsen cells, yielded information related to the processes of ion formation. For the reaction Na2(CN)2(g)=2NaCN(g),we obtain ΔH1000°=41.0±3.0 kcal/mole dimer. This indicates a dimer stability comparable to that for Na2I2(g).