Abstract
The dissociation pressure of nickel sulphate in the absence or presence of ferric oxide has been measured by means of the dynamic gas-solid technique. In the experiments, nickel sulphate or nickel ferrite was placed in a stream of SO2-O2-N2 gas mixtures with SO3 potentials controlled. Thermogravimetry (the furnace temperature was slowly raised) was used as a detection method.The results of the measurements of nickel sulphate lead to the dissociation pressure equation:NiSO4=NiO+SO3logρSO3=-12476/T+9.98 (atm)ThusΔG°=57080-45.66T (cal)These results well agreewith the previous results obtained from the static measurements.With the increase of temperature, the nickel ferrite changes through the following steps:Nio·Fe2O3→Fe2(SO4) 3, NiSO4→Fe2O3, NiSO4→NiO·Fe2O3ThusNiSO4+Fe2O3= NiO·Fe2O3+SO3logpSO3= -11370/T =9.22 (atm)ΔG°·=52020 -42.16T (cal)From the standard free energy data of the decomposition of nickel sulphate in the absence or presence of ferricoxide, the standard free energy of formation of nickel ferrite has been obtainedas follows:NiO+Fe2O3 =Nio·Fe2O3ΔG°=-5060+3.5T (cal)
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