Solid nickel sulphates

Bell [40BEL] reported vapour pressure measurements that showed that at 

15 K removal of water from NiS04-7H20(cr) is less favoured than removal of D2O from NiS04 7D20 (see Appendix A). In this review, no values are selected for the thermodynamic quantities of NiS04-7D20. 

The more extensive set of measurements by Goldberg et al. resulted in more dilute final solutions of nickel sulphate, and are preferred here. Goldberg et al. used enthalpy of dilution values of Lange [59LAN] and Lange and Miederer [56LAN/MIE] to extrapolate the enthalpy of solution to / = 0, and obtained = 4.81 kJ mol (as is normal 

The value of AfG° (NiS04-6.00H20, a, 298.15 K) is calculated from the selected values of Af77° (NiS04 6.00H20, 298.15 K) and 5 (NiS04-6.00H20, a, 

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Hexammino-niekel Sulphate, [Ni(NH3)e]S04.—Anhydrous nickel sulphate rapidly absorbs ammonia gas, heat is developed, and a bulky white powder produced of composition NiS04.6NH3. It is soluble in water, forming a blue solution and a precipitate of green nickel hydroxide. The solid when heated decomposes with loss of ammonia.2... 

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]. 

Results of study of the decomposition of nickel sulphate heptahydrate through nickel sulphate hexahydrate and nickel sulphate tetrahydrate at 0.015 bar (II torr) are presented. X-ray diffraction patterns are presented for some of the different solids. Detailed measurement results were not tabulated, but the graphical presentation and the reported thermodynamic quantities for the dehydration reactions are in reasonable agreement with results reported in the later study of Kohler and Zaske [64KOH/ZAS]. 

Sulphur attack on nickel-chromium alloys and nickel-chromium-iron alloys can arise from contamination by deposits resulting from the combustion of solid fuels, notably high-sulphur coals and peat. This type of corrosion, which has been observed on components of aircraft, marine and industrial gas turbines and air heaters, has been associated with the presence of metal-sulphate and particularly sodium sulphate arising directly from the fuel or perhaps by reaction between sodium chloride from the environment with sulphur in the fuel. Since such fuels are burned with an excess of air, corrosion occurs under conditions that are nominally oxidising although the deposits themselves may produce locally reducing conditions. 

The ash deposits resulting from the combustion of solid and oil fuels often contain appreciable quantities of other corrodants in addition to vanadium pentoxide. One of the more important of these is sodium sulphate, and the effects of this constituent in producing sulphur attack have been mentioned. The contents of sodium sulphate and vanadium pentoxide present in fuel oil ash can vary markedly and the relative merits of different materials depend to a great extent upon the proportions of these constituents. Exposure of heat-resisting alloys of varying nickel, chromium and iron contents to ash deposition in the super-heater zones of oil-fired boilers indicated a behaviour pattern depending on the composition of the alloy and of the ash... 

Nienow and Conti (1978) developed a model of particle abrasion at high solids concentration based on Rittinger s law of comminution. When tested experimentally using copper sulphate and nickel ammonium sulphate crystals in two non-solvent liquids, measured abrasion rates were consistent with a second-order dependence of concentration as predicted (Figure 5.12). 

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