"An experimental investigation was conducted in order to determine the thermodynamic and kinetic behavior of the system PbO-PbS.
The thermodynamic behavior of the system PbO-PbS was studied by measuring the PSO₂ in argon-SO2 mixtures equilibrated with various PbO-PbS mixtures in a recirculating-type equilibrium apparatus, and analyzing the condensed phases by means of X-ray diffraction.
The effect of temperature and PbO/PbS ratio on the rate of SO2 evolution was investigated in order to determine the reaction mechanisms involved in the approach to equilibrium.
A sodium hydroxide, hydrogen peroxide titration technique was employed in the analysis of SO2 in the gas mixtures.
A detailed description of the apparatus and experimental procedure is given for both the equilibrium and kinetic studies.
At constant temperature the variation of PSO₂ with composition was found to consist of several horizontal lines connected by diagonal lines. Below 733°C the isotherms consisted of two horizontals connected by one diagonal line. Above 733°C the isotherms consisted of three horizontals connected by two diagonal lines. X-ray analysis of the condensed phases showed that the horizontals represented areas of three-phase stability and the diagonal lines areas of two-phase stability.
A phase diagram was constructed for the system PbO-PbS. The equilibrium results indicated the presence of liquid solubility in lead and solid-solubility in the basic sulfates; however, the exact composition of the liquid lead and the basic sulfates was not determined. The Pb-S-O diagram, proposed by Kellogg and Basu, has been corrected to coincide with the PbO-PbS diagram from this investigation.
A linear free energy equation was derived for the ΔF°f of PbSO4• 4PbO in the temperature range 700°-760°C. Additional calculations were made for the ΔH°f and ΔS°f of PbSO4• 4PbO. The calculations from the experimental results agreed very well with the calculations made from the data of previous investigators.
The kinetic studies indicated that the reaction mechanism in the system PbO-PbS is (1) conversion of all of the PbO or PbS (whichever is the minor constituent) to either PbSO4• 4PbO or PbSO4• 2PbO, and (2) reaction between the basic sulfate and either Pb or PbS to produce SO2.
From the results of this investigation it was established that the equilibrium 2PbO + PbS ⇋ 3Pb + SO2, which was thought to be the basis of ore-hearth smelting, is unstable at all PbO/PbS ratios in the temperature range 700°-760°C"--Abstract, pages i-iii.
Schlechten, A. W.
Lorey, G. Edwin
Larson, Andrew H.
Planje, Theodore J., 1919-1980
Materials Science and Engineering
M.S. in Metallurgical Engineering
Missouri School of Mines and Metallurgy
x, 126 pages
© 1960 John P. Hager, All rights reserved.
Thesis - Open Access
Lead compounds -- Analysis
Lead compounds -- Heat treatment
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Hager, John P., "A thermodynamic study of the system PbO-PbS" (1960). Masters Theses. 2672.