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 $${\mathrm{Na}}_2(\mathrm{CN}{)}_2(\mathrm{g}\text{)=2}\mathrm{NaCN}(\mathrm{g}\mathrm{),}$$ we obtain ΔH₁₀₀₀°=41.0±3.0 kcal/mole dimer. This indicates a dimer stability comparable to that for Na₂I₂(g).