Coordination precipitate method

In this paper, the nano Ni(OH)2 powders were prepared by the coordination-precipitation method. The effect of the experimental parameters on the phase composition and structure, such as the precipitating agent concentration, the reaction temperature and the coordination agent quantity has been discussed. 

Coordinated Phosphate Method. In this method of treatment, no free caustic is maintained in the boiler water. Fig. 10 shows the phosphate concentration versus die resulting pH when trisodium phosphate is dissolved in water. Recent laboratory tests show that the crystals which precipitate from a concentrated solution of trisodium phosphate at elevated temperatures contain disodium phosphate and that the supernatant liquid is rich in sodium hydroxide. The sodium hydroxide can destroy the magnetite protective film on boiler surfaces. To assure that no free caustic is present, a boiler-water phosphate concentration thal corresponds Lo a sodium-lo-phosphate mole-ratio of 2.6 is recommended above 1000 psi (68 atm), as... 

The discovery of nuclear fission in 1938 proved the next driver in the development of coordination chemistry. Uranium-235 and plutonium-239 both undergo fission with slow neutrons, and can support neutron chain reactions, making them suitable for weaponization in the context of the Manhattan project. This rapidly drove the development of large-scale separation chemistry, as methods were developed to separate and purify these elements. While the first recovery processes employed precipitation methods (e.g., the bismuth phosphate cycle for plutonium isolation). 

The nickel molybdate catalyst used in this study, prepared by the precipitation method described by Mazzocchia [4], has been supplied by Elf Atochem (France). The bulk Mo / Ni ratio in this solid is practically equal to 1 it can exist as phases a and P, differing by the coordination of Ni ions. Only the results for the a form will be reported here. The specific surface area as measured by N2 adsorption is about 40 m / g. 

Boron trifluoride catalyst may be recovered by distillation, chemical reactions, or a combination of these methods. Ammonia or amines are frequently added to the spent catalyst to form stable coordination compounds that can be separated from the reaction products. Subsequent treatment with sulfuric acid releases boron trifluoride. An organic compound may be added that forms an adduct more stable than that formed by the desired product and boron trifluoride. In another procedure, a fluoride is added to the reaction products to precipitate the boron trifluoride which is then released by heating. Selective solvents may also be employed in recovery procedures (see Catalysts,regeneration). 

The important oxides are black PdO and brown Pt02. The former can be made by heating palladium in oxygen other methods include heating PdCl2 in an NaN03 melt at 520°C. A hydrated form precipitates from aqueous solution, e.g. when Pd(N03)2 solution is boiled. It has 4-coordinate square planar palladium (Figure 3.8). 

Searching for ways of getting rid of these products, a method was worked out by which their decomposition was induced under strictly controlled conditions. Decomposition is caused, ifor instance, by pouring the mixture into hot water after nitration. The amount of water and the temperature are coordinated so that a concentration of 50-55% HN03 and a temperature of 70-90°C are maintained. Highly pure cyclonite is precipitated and N02 evolved from the decomposition of all unstable products. This is the so-called degassing process . 

The study of coordination compounds of the lanthanides dates in any practical sense from around 1950, the period when ion-exchange methods were successfully applied to the problem of the separation of the individual lanthanides,131-133 a problem which had existed since 1794 when J. Gadolin prepared mixed rare earths from gadolinite, a lanthanide iron beryllium silicate. Until 1950, separation of the pure lanthanides had depended on tedious and inefficient multiple crystallizations or precipitations, which effectively prevented research on the chemical properties of the individual elements through lack of availability. However, well before 1950, many principal features of lanthanide chemistry were clearly recognized, such as the predominant trivalent state with some examples of divalency and tetravalency, ready formation of hydrated ions and their oxy salts, formation of complex halides,134 and the line-like nature of lanthanide spectra.135... 

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