Nickel ammonium sulphate

Nickel sulphate yields numerous double salts. Of these the most important is Nickel Ammonium Sulphate (NH4)2S04.NiS04.6H,0, which is largely used in electroplating. It is readily prepared by adding the requisite quantity of ammonium sulphate to a concentrated solution of nickel sulphate in dilute sulphuric acid. It crystallises in bluish green monoclinic prisms. These are less soluble than the corresponding cobalt salt. 

Anhydrous Nickel Ammonium Sulphate, 3NiS04.2(NH4)2S04, has been prepared by fusing together 5 nickel sulphate, oxide, hydroxide, or carbonate and excess of ammonium sulphate. It combines with water evolving heat. When ignited, anhydrous nickel sulphate remains behind. 

Fig. 4. Results from the nucleation kinetic studies on nickel ammonium sulphate. A, Homogeneous nucleation B, heterogeneous nucleation , experimental data. (Reproduced from ref. 10 by courtesy of The Royal Society of Chemistry.)...

In making double salts, it is probable that better results are obtained if both components are put into solution separately rather than that one should be dissolved in a concentrated solution of the other. The observations may be baseless, but I have always thought for instance, that superior crystals of nickel-ammonium sulphate were produced by bringing both single sulphates into solution separately. —Editor. 

Mixtures op Copper Ammonium Sulphate and Nickel Ammonium Sulphate in Water at i3°-i4 . 

Much lower values of 7 are expected for soluble salts. The data in Figure 5.16 for nickel ammonium sulphate, where /md was determined visually (Mullin and Osman, 1973 Mullin and Ang, 1976), again show a homogeneous/hetero-geneous division, this time at a value of 1.8, and a value of 7 4mJm is calculated from data in the left hand region for S > 2. 

The temperature dependence of interfacial tension has been demonstrated using induction period data for nickel ammonium sulphate recorded over a short temperature range. The salt was precipitated by quickly mixing equimolar solutions of nickel and ammonium sulphates after which the system was allowed to remain static until nucleation occurred. Plots of log/md versus T (log S) , in accordance with equation 5.38, gave a family of straight lines... 

Figure 5.16. Induction period as a function of initial super saturation for nickel ammonium sulphate. A = homogeneous, B = heterogeneous nucleation. After Mullin and Ang, 1976)...

Salts that have been established as having solution velocity dependent growth rates include ammonium and potassium alums, nickel ammonium sulphate, sodium thiosulphate and potassium sulphate. Ammonium sulphate, ammonium and potassium dihydrogen phosphates, for example, do not. 

Desupersaturation methods for crystal growth rate measurements have been reported for ammonium alum (Bujac and Mullin, 1969), potassium sulphate (Jones and Mullin, 1973a), nickel ammonium sulphate (Ang and Mullin, 1979), potassium chloride (Nyvlt, 1989) and succinic acid (Qui and Rasmuson, 1990). 

In addition to confirming the well-known beneficial effect of using reasonably dilute reactants to produce coarse precipitates, the laws demonstrate that excessive dilution can be detrimental, a fact that is not always fully appreciated. Experimental evidence for the Weimam laws has been provided by Mullin and Ang (1977) for the precipitation of nickel ammonium sulphate. 

Ang, H-M. and Mullin, J.W. (1979) Crystal growth rate determinations from desupersaturation measurements nickel ammonium sulphate hexahydrate. Transactions of the Institution of Chemical Engineers, 57, 237-242. 

Mullin, J.W. and Ang, H-M. (1976) Nucleation characteristics of aqueous nickel ammonium sulphate solutions. Faraday Society Discussions, No. 61, 141-148. 

Mullin, J.W. and Osman, M.M. (1973) Nucleation and precipitation of nickel ammonium sulphate crystals from aqueous solution. Kristall und Technik, 8, 471-481. 

J. W. Mullin and H.-M. Ang, Supersaturation and crystal size distribution changes during the precipitation of nickel ammonium sulphate hexahydrate, Kristall und Technik, 12 (1977), 105-115. 

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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