Marcel Ackerman

Mass spectrometric determination of the dissociation energies of the molecules AgAu, AgCu, and AuCu

Abstract : The vapors issuing from mullite and Grpahite Knudsen cells containing pure metals and alloys of the triad Cu-Ag-Au have been analyzed mass spectrometrically. From the experimental ratios of diatomic to monoatomic species and the vapor pressures of the elements, the following dissociation energies are obtained: Cu2 = 43.2 + or - 2.2 kcal; AgAu = 47.6 + or - 2.2 kcal; Ag2 = 35.7 + or - 2.2 kcal; AgCu = 40.7 + or - 2.2 kcal; Au2 = 51.9 + or - 2.2 kcal; AuCu = 54.3 + or -2.2 kcal. These are based on H (sup vap) (sub 298) = 81.1, 68.4 and 87.5 cal/mole for Cu, Ag and Au where dissociation energy of AgAu depends on the value for Cu, and dissociation energy of AgAu and AuCu on Au. The uncertainties quoted do not include the uncertainty in Delta H (sup vap). These results are interpreted in terms of chemical bonding theories. The relation between bonding in the gas and in the pure condensed phases is again observed. Furthermore, a previously unobserved qualitative relation between the dissociation energy of the asymmetrical molecule and the heat of formation of the corresponding alloys is indicated.

Mass Spectrometric Study of the Gaseous Molecules above AgSn, AuSn, and CuSn Alloys

Mass spectrometric technique has been employed to analyze the molecular beams effusing from mullite Knudsen cells containing Sn and alloys of Cu, Ag, and Au with Sn. From the experimental intensities of monatomic and diatomic species and the vapor pressure of Sn, the following dissociation energies are obtained: D0∘(Sn2)=45.8±4 kcal/mole,D0∘(AgSn)=31.6±5 kcal/mole,D0∘(AuSn)=57.5±4 kcal/mole,D0∘(CuSn)=41.4±4 kcal/mole.

Studies of the Vapors of the System Au–Cr and Au–Pd by Mass Spectrometry

The molecules AuCr and AuPd have been identified. From data for the reaction Au2+X=AuX+Au, and D0°(Au2)=51.5 kcal/mole: D0∘(AuCr)=50.4±3.5 kcal/mole,D0∘(AuPd)=33.3±5 kcal/mole.