Other hydrated nickel sulphate solids

Solubility data [34BEN/THI], [39ROH] indicate that the P-hexahydrate is the stable solid in contact with saturated solutions of nickel sulphate in water for temperatures between 325 and 358 K, where lower hydrates begin to predominate. As might be expected, addition of sulphuric acid results in the appearance of the lower hydrates at lower temperatures [39ROH]. 

Based on their differential scanning calorimetry results. Rubbering et al. [75RAB/WAN] reported A 77 = (6.53 0.17) kJ-mol for the reaction  

Rabbering et al. [75RABAVAN] and Siracusa et al. [78S1R/SEM] carried out thermal decomposition studies by a variety of techniques, and found evidence for decomposition of the P-hexahydrate to a tetrahydrate at temperatures near 400 K and to the monohydrate near 440 K. Nandi et al. [79NAN/DES] found that the dehydration pattern for thermogravimetric measurements carried out at 5 K min were different for well-crystallised and powdered samples of the heptahydrate and hexahydrate. However, the intermediate hydrates were not well characterised. 

Although Goldberg et al. [66GOL/R1D] indicated that samples of NiS04(cr) dissolved too slowly in water to allow determination of its heat of solution, Adami and King [65ADA/KIN] reported the heat of solution in 4.360 m HCl(aq) at 303.15 K. The thermodynamic cycle involved comparison with the heat of dissolution of metallic nickel in a similar medium. The results of [65ADA/KIN] have been recalculated in the present review (Appendix A) to obtain the selected value  

Weller [65WEL] measured the heat capacity of anhydrous nickel sulphate between 52.0 and 296.3 K. Stuve et al. [78STU/FER] also measured the heat capacity by adiabatic calorimetry, but primarily at lower temperatures, between 9.7 and 69.6 K (a 

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