First period transition metal sulphates

Rising temperature measurements, supplemented by isothermal studies, gave values of E, based on obedience to the contracting volume equation [eqn. (7), n = 3], ranging from 96 to 123 kJ mole 1 and increasing in the sequence Zn Fe(III) Co Ni Cu. 

MnS04 decomposes in nitrogen (1073—1173 K) to Mn304 and in oxygen (1123—1173 K) to Mn203 values of E, based on rates of initial reaction, were 213 and 259 kJ mole 1, respectively [778]. 

Although the decompositions of FeS04 and Fe2(S04)3 have received considerable attention, there is a lack of close agreement between isothermal and non-isothermal measurements [528]. Kinetic parameters are sensitive to the nature of the prevailing atmosphere and the particular salt preparation used [381]. The decomposition of iron(II) sulphate [319, 381,524] in vacuum or in an inert atmosphere (748—848 K) proceeds with the transitory formation of the intermediate Fe202(S04), viz. 

NiS04 decomposes directly to NiO between 968 and 1083 K [784] (the oxide product may undergo some further dissociation [770]). The value of E determined from the region of constant reaction rate (269 8 kJ mole-1) is in satisfactory agreement with that reported by Ingraham and Marier [785] (225 12 kJ mole-1) at 1273—1423 K. 

The intermediate formed in the two-stage decomposition of ZnS04 to ZnO has been variously reported as Zn502(S04)3 [781,798] and Zn30(S04)2 [784,799] reported values of E (Table 15) show little consistency. Decomposition has been described [799] as a topochemical reaction and the reverse process is slow if the ZnO (product) is not finely divided. 

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