Nickel hydroxide solution, measurement

Nickel may he measured quantitatively hy several microanalytical gravimetric methods that include (l)formation of a red precipitate with dimethyl-glyoxime, (2) precipitation as a hlack sulfide with ammonium sulfide, (3) precipitating as a complex cyanide hy treating with alkali cyanide and bromine, and (4) precipitation as a yellow complex hy treating an ammoniacal solution of nickel with dicyandiamide sulfate (Grossman s reagent), followed hy the addition of potassium hydroxide. All of these methods can separate nickel from cobalt in solution. 

The detection step involves electrochemical oxidation at a nickel electrode. This electrode has been applied to measurements of glucose (4), ethanol (5), amines, and amino acids (6,7). The reaction mechanism involves a catalytic higher oxide of nickel. The electrolyte solution consists of 0.1 M sodium hydroxide containing 10-4 M nickel as suspended nickel hydroxide to ensure stability of the electrode process. The flow-injection technique offers the advantages of convenience and speed in solution handling and ready maintenance of the active electrode surface. 

In the reduction of nitrobenzene in a 2% aqueous sodium-hydroxide solution, according to previous publications, azoxy-benzene is formed at platinum and nickel electrodes, azobenzeno at lead, tin, and zinc cathodes, and aniline at copper cathodes especially in the presence of copper powder. It was found that, in an unchangeable experimental arrangement, a cathodo potential of 1.8 volts, as measured in connection with the deci-normal electrode, could be carried out with all the chosen cathodes and additions. At this constant potential, by using different metals and adding various metallic hydroxides, the whole reduction was carried out and the nature and quantity of the reduction products determined in each case. It turned out that the emphasized differences in the results disappeared and that, with an equal potential of all cathodes, similar yields of azoxybenzene and aniline and traces of azobenzene resulted. The cathodes were of platinum, copper, copper and copper powder, tin, platinum with addition of stannous hydroxide zinc, platinum with addition of zinc hydroxide, lead, platinum with addition of lead hydroxide, and nickel. The yields of azoxybenzene varied from 41-65% of aniline 23-53%. 

This paper describes some of our initial studies of the solution properties of sodium titanate powders in order to understand and control the metal-loading process in the preparation of a heterogeneous catalyst from the materials. The purposes of this study are 1) to define the pH and concentration regimes in which nickel is loaded onto sodium titanate as monomeric ions via ion exchange, as polymeric clusters via hydrolysis, or as discrete particles of colloidal nickel hydroxide, and 2) to characterize the catalysts with respect to the dispersion of the active metal under reaction conditions by measuring the activity and selectivity of the catalysts for a known "structure-sensitive" reaction, the hydrogenolysis of n-butane. 

Hydrous sodium titanate was prepared by the method of Dosch and Stephens (1). Titanium isopropoxide was slowly added to a 15 wt% solution of sodium hydroxide in methanol. The resulting solution was hydrolyzed by addition to 10 vol% water in acetone. The hydrolysis product is an amorphous hydrous oxide with a Na Ti ratio of 0.5 which contains, after vacuum drying at room temperature, approximately 13.5 wt% water and 2.5 wt% residual alcohol. The ion-exchange characteristics of the sodium titanate and the hydrolysis behavior of the nickel nitrate solutions were characterized using a combination of potentiometric titrations, inductively coupled plasma atomic emission (ICP) analysis of filtrates, and surface charge measurements obtained using a Matec electrosonic amplitude device. 

Raney-type nickel catalysts are typically prepared by leaching aluminium from a Ni-Al alloy using a concentrated sodium hydroxide solution [1-3], This process of activation critically affects the structure and properties of Raney-type nickel catalysts. The initial structure and composition of the starting alloy also influence the performance of the final catalyst [4-7], In this paper, numerical modelling is compared to experimental measurements in an attempt to simulate both the 3D morphology of as-leached Raney-Ni catalyst material and investigate the nature of the exposed catalyst surfaces. 

Three titrations of pure as well as NaCl- or Na2S04-containing nickel nitrate solutions with sodium hydroxide were carried out at 25°C. From the pH measured at each point taken on the titration curve (0.07 < (NaOH) / (Ni(N03)2) 1.62) the solubility product was calculated and extrapolated to zero ionic strength. A mean value of log,g K°f, = - 14.50 was obtained and has been taken as a basis for the value listed in Figure V-11 and Table V-6, respectively. 

Transfer to a 100-ml measuring flask either 50 ml of the water sample or a smaller quantity which has been made up to 50 ml with distilled water (nickel content 0.001 to 0.25 mg). Add 10 ml of bromine water and shake. Add one after the other 8 ml of triethanolamine, 12 ml of concentrated ammonium hydroxide solution and ml of diacetyl dioxime solution and... 

Next treat the hydrochloric solution containing the nickel with 3 ml of diacetyl dioxime solution, 1 ml of 10 m sodium hydroxide solution and 0.3 ml of ammonium peroxodisulphate solution, mixing well each time. Dilute with water to the mark at 20 C, leave to stand for about 2 hours, and measure in a 3-cm cuvette at 60 nm against distilled water. Carry out a blank test concurrently and take into account accordingly. 

If minute quantities of electricity are to be measured the electrolytic gas coulometer is recommended in this case a 15 per cent solution of sodium hydroxide is used as electrolyte while the electrodes are of platinum or nickel. Both the hydrogen and the oxygen escaping from the closed electrolytic cell... 

Figure 10. Precipitation of nickel(II) from a homogeneous solution by injection of sodium hydroxide at 293 K. A measurement without suspended alumina and measurement with suspended alumina are represented. The final nickel loading is indicated in the figure [I8J.

An electrochemical cell consists of a nickel metal electrode immersed in a solution with [Ni2+] = 1.0 M separated by a porous disk from an aluminum metal electrode immersed in a solution with [Al3+] = 1.0 M. Sodium hydroxide is added to the aluminum compartment, causing AI(OH)3(s) to precipitate. After precipitation of Al(OH)3 has ceased, the concentration of OH- is 1.0 X 10-4 M and the measured cell potential is 1.82 V. Calculate the Ksp value for Al(OH)3. 

Organic gels were prepared by polycondensation of resorcinol with formaldehyde in water as a solvent. Three series of carbon samples were prepared one without addition of metal the two others containing nickel and palladium (about 1% weight) respectively. The incorporation of metal was achieved by dissolution of a metal salt nickel acetate (tetrahydrate) and palladium acetate were used. As resorcinol plays the role of nickel complexant, nickel is easily soluble in resorcinol-formaldehyde aqueous solutions. On the contrary, significant amounts of palladium cannot be dissolved without using an additional complexant. Diethylenetrinitrilopentaacetic acid (DTPA) was then added to the solution. No sodium carbonate as polymerisation catalyst was used. In this work, the pH was adjusted to a chosen value by the use of sodium hydroxide (aqueous solution) and measured by a pH-meter. 

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