Richard C. Schoonmaker

Mass Spectrometric and Thermodynamic Study of Gaseous Transition Metal (II) Halides

Mass spectrometric and Knudsen effusion techniques have been used to study the vaporization of several transition metal (II) halides. The systems studied include FeI2 and the chlorides and bromides of Cr, Mn, Co, and Ni. The over‐all temperature range was between 440 and 700°C. For all systems the monomer is the major vapor species in the temperature range studied. Dimeric species have also been detected in the vapor phase for all systems, except NiCl2 and NiBr2. Vapor pressure data have been combined with mass spectrometric and entropy data to give heats for the dimerization reaction, 2MX2 (g)=M2X4 (g).

Mass Spectrometric Study of the Vaporization of LiF, NaF, and LiF–NaF Mixtures

Vapors effusing from Knudsen cells containing LiF, NaF, and LiF–NaF mixtures have been analyzed mass spectrometrically. The over‐all temperature range studied is between 900 and 1150°K. Monomers, dimers, and trimers of LiF and NaF are observed. The LiF system has the higher concentration of dimers and trimers. In the LiF–NaF system at 50 mole percent LiF the mixed dimer, LiNaF2, is the major polymeric vapor species. Thermochemical data for LiF(g), NaF(g), Li2F2(g), Na2F2(g) and Li3F3(g) have been obtained. For the reaction Li2F2(g)+Na2F2(g)=2LiNaF2(g), ΔH° is approximately zero.

Heats of Dimerization of Alkali Fluoride Molecules

A mass spectrometer has been used to analyze vapors in equilibrium with alkali fluoride condensed phases. Monomers, dimers, and trimers have been detected in all alkali fluoride vapors. In addition to monomers and dimers characteristic of pure condensed phases, mixed dimers were found in equilibrium with mixed condensed phases. A method for determining the difference in dimerization energies for constituents in a mixed vapor has been formulated, and dimerization enthalpies for alkali fluoride species are presented.

Mass Spectrometric Study of Ferrous Chloride Vapor

Mass spectrometric studies of the vaporization process of ferrous chloride show that the major vapor species is monomeric FeCl2(g). A small concentration of Fe2Cl4(g) is present in the vapor at low temperatures. The ratio of dimer to monomer concentration increases rapidly with temperature showing that at the melting point of FeCl2(s), the equilibrium vapor consists of about 25% dimer. Thermodynamic treatment of ion current data yields for the reaction 2FeCl2(s)=Fe2Cl4(g),ΔH640∘K∘=56±3 kcal/mole of dimer and for the reaction Fe2Cl4(g)=2FeCl2(g),ΔH640∘K∘=32±3 kcal/mole of dimer.

Gaseous Species in the Vaporization of Sodium Hydroxide

Mass spectrometric studies of the gaseous species in sodium hydroxide vapor have shown that in the temperature range 300°C to 450°C, NaOH (1) vaporizes mainly as gaseous dimers. A thermodynamic treatment of ion current data yields for the reactions: 2NaOH(l)=Na2(OH)2(g)ΔH660∘K0=28±3 kcal/mole of dimerNaOH(s)=NaOH(g)ΔH298∘K0=46.4±3 kcal/mole of NaOH2NaOH(g)=Na2(OH)2(g)ΔH660∘K0=−54±5 kcal/mole of dimer. Comparison with existing data on the gaseous alkali halides shows the trend in dimerization energies: NaOH(g)>NaCl(g)>NaF(g).

Mass Spectrometric Study of Alkali Hydroxide Vapors

A mass spectrometer has been used to analyze the vapors effusing from the orifice of a Knudsen cell containing pure and mixed alkali hydroxide condensed phases. Monomeric and dimeric species are detected in all cases except for LiOH in the temperature range 650–900°K. Thermochemical data are reported for the reactions 2MOH(g)=M2(OH)2(g),and M2(OH)2(g)+N2(OH)2(g)=2MN(OH)2(g), where M and N represent constituent alkali metals. The analogous behavior of the vaporization processes of alkali fluorides and hydroxides is discussed.