| Description |
ix, 92 leaves : illustrations, photographs ; 29 cm |
| Summary |
"The influence which ZnS, CdS, Cu₂S, PbS, and FeS has on the thermal decomposition rate of ZnSO₄ was studied by measuring the SO₂ gas evolved per unit of time for various ZnSO₄-MeS mixtures at 600°C, and analyzing the solid phases by means of X-ray diffraction patterns. The SO₂ gas evolved upon heating the pellets was analyzed as a function of time by absorbing the gas in a solution of distilled water, H₂O₂, and NaOH, and measuring the time required for the SO₂ to neutralize the NaOH. The gas absorption was found to be accurate and reproducible. The thermal decomposition of ZnSO₄ occurred through the formation of several basic sulfates (xZnO·yZnSO₄). The basic sulfate formed at 600°C was identified as ZnO·2ZnSO₄. The admixtures markedly increased the decomposition rate of ZnSO₄. The rate of reaction for mole:mole mixtures of ZnSO₄ and ZnS, CdS, and Cu₂S was approximately identical. The decomposition of the sulfate was much more rapid with PbS and FeS. One step that the ZnS, CdS, and Cu₂S systems had in common was the formation of the intermediate phase ZnO·2ZnSO₄. The faster PbS and FeS reactions passed through no basic sulfate formation step. The decomposition of the basic sulfate was shown to be the rate determining step. The following steps were proposed for the ZnS, CdS, and Cu₂S systems: (1) The formation of oxide(s) or sulfate (fast). (2) The formation of the basic sulfate, ZnO·2ZnSO₄ (fast). (3) The decomposition of the basic sulfate (slow). The d values and relative intensities of the experimental X-ray diffraction pattern for the ZnO·2ZnSO₄ phase are reported"--Abstract, leaves i-ii. |
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