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The second virial coefficients of He' and He4 have been calculated at closely spaced temperatures over the range 0. 3'K to 60'K using the Lennard-Jones 12 -6 potential with constants determined by de Boer and Michels. The necessary phase shifts were calculated on a high-speed electronic digital computer. The resulting He4 second virial coefficients agree very well with the available experimental data. They also join nicely at 60'K with the coeKcients calculated from the high-temperature. classical equation with quantum corrections. The second cross virial coefficients for He3, He4 have also been calculated. The deviation of a gaseous solution of He3 and He4 from an ideal solution is comparatively small at temperatures above about 2'K, while at very low temperatures pronounced quantum solution imperfection appears.

The infrared and Raman spectra of liquid and solid nitric oxide have been studied in an attempt to prove the existence of the (NO)2 molecule. The liquid has four strong Raman lines at 1861, 262, 196, and 167 cm−1; two weaker Raman lines at 1760 and 487 cm−1; and two strong infrared bands at 1863 and 1770 cm−1. Several weaker infrared bands can be satisfactorily assigned as combinations by using the observed strong infrared and Raman frequencies. The spectra were found to be due exclusively to a dimer which probably exists as a bent ONNO molecule.