Dissolution Kinetics of Nickel(II) Hydroxide in a Mixed Ammonia–Carbonate Solution

Theoretical Foundations of Chemical Engineering - The reaction of nickel(II) hydroxide and a mixed ammonia–carbonate solution to form nickel(II) aqua–ammonia complexes is studied in the...     

Effect of the Charge of Solid Particles on the Activation Energy of Acid Decomposition of Phosphorus-Containing Raw Material

Experimental data on the effect of ionogenic surfactants on the charge of fluorapatites and hydroxyapatites in aqueous solutions are analyzed. The effect of cetylpyridinium chloride (a cationic surfactant) and sodium dodecyl sulfate (an anionic surfactant) on the activation energy of decomposition of phosphate raw material by nitric, sulfuric, and phosphoric acids is experimentally studied. It is shown that, regardless of the nature of the solid and liquid reactants, the activation energy is minimal in the isoelectric state of the surface of the solid-phase particles.__________Translated from Teoreticheskie Osnovy Khimicheskoi Tekhnologii, Vol. 39, No. 4, 2005, pp. 440–443.Original Russian Text Copyright © 2005 by Dobrydnev, Bogach, Kol’tsova, Beskov.     

Analysis of the Mass Transfer in Acid Decomposition of Phosphorus-Containing Raw Material

Experimental data on the effect of surfactants on the rate of acid decomposition of apatites are discussed using the mathematical tools of systems analysis of chemical engineering processes (synergetic method). An analytical expression relating the mass-transfer rate to the interfacial electrical properties is derived. It is shown that the limiting step in decomposition of fluorapatite and hydroxylapatite by nitric, sulfuric, and orthophosphoric acids is the mass transfer from the surface layer into the bulk of the solution.     

The epidural use of morphine and alpha 2-agonists for postoperative analgesia

Three protocols of postoperative pain relief after gastric surgery were used in 60 male patients: regular intramuscular morphine, epidural morphine, and epidural morphine with 0.1 mg of clonidine. Pain relief was more effective with the epidural route of administration. Addition of clonidine in a daily dose of 0.1 mg allowed a twofold decrease of epidural morphine dose, involving lesser hyperdynamic postoperative cardiovascular changes and complete elimination of psychotic complications and delirium in alcohol-dependent patients.     

Ionometric Study of the Acid Decomposition of Phosphate Minerals

A setup allowing computer processing of experimental data is suggested for studying the acid decomposition of phosphate minerals. A potentiometric technique using ion-selective electrodes is proposed for determining the starting substances and reaction products in solution.     

Influence of Surfactants on the Rate of Decomposition of Apatites by Mineral Acids

The dependence of the true rate of decomposition of fluorapatite and hydroxylapatite in nitric, sulfuric, and orthophosphoric acids on the concentration of a surfactant (cetylpyridinium chloride and sodium dodecyl sulfate) was experimentally studied. The electrokinetic potential in the slip plane of the double electric layer at the interface between apatite and an aqueous solution of a surfactant was measured by the electroosmotic method. The concentrations of cetylpyridinium chloride (5.5 × 10^–6 mol/l) for fluorapatite and sodium dodecyl sulfate (1 × 10^–4 mol/l) for hydroxylapatite were found, which correspond to the isoelectric state of the surface of the solid phase. It was established that the true rate of decomposition of apatites is maximal when the electrokinetic potential is zero.