摘要:

AbstractA theoretical approach to the problem of how contact leaching anti‐fouling paints work is discussed; a possible mechanism is selected and applied to an idealised model of a paint film. A precise mathematical treatment is then attempted of the relationship between the leaching rate, the physical properties, and if applicable the chemical properties of the envisaged paint film and its environment. A mechanism previously proposed has been examined by this method. An equation is derived for an idealised paint film relating the leaching rate to the physical properties of the paint film and the leachate. It is assumed that the rate of solution of a soluble pigment from an insoluble vehicle is dependent only on the physical properties of the paint film and the diffusion of the solvated pigment through the exhausted matrix and the diffusion layer of leachate in direct contact with the surface of the paint. An equation is derived for an idealised paint film which relates the leaching rate to some physical properties of the paint film and of the leachate.The equation is shown to predict qualitatively the effect of most variables known to affect the leaching of contact leaching paints. Some evidence is given to support the quantitative prediction of the relationship between the pigment volume content and the initial leaching rate, the effect of dissolved pigment in solution on the leaching rate, the increase in leaching rate for a given temperature increase, and the effect of velocity of flow past the surface of the paint film.This method of approach would appear to be applicable to mechanisms and models bearing a closer resemblance to practical anti‐fouling paints. However, the mechanism proposed appears sufficiently well substantiated to be employed in the design of leaching experiments and their application to more practical problems, such as the formulation of anti‐fouling paints.The need of a more rigorous approach to the design of leaching experiments is indi

ISSN:0021-8871    

DOI:10.1002/jctb.5010190401

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractEvidence from specific‐ion electrode and conductivity measurements at 25° confirms that sodium fluorosilicate, at the concentration normally present in public water supplies, is dissociated to at least 95%. The degree of dissociation at other concentrations up to 3,000 ppm as fluoride, is shown to be markedly lower than previous kinetic experiments had suggested. The dissociation of fluorosilicic acid has also been investigated using the same techniques, and the results obtained closely follow the pattern established for the sodium sa

ISSN:0021-8871    

DOI:10.1002/jctb.5010190402

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractLiquid‐liquid equilibrium data were obtained at 25° for the distribution of copper, cobalt and nickel between aqueous sulphate solutions and kerosene solutions of di‐(2‐ethyl hexyl) phosphoric acid (EHPA). Two mechanisms of extraction were observed. When the ratio (L) of organic phase equilibrium metal concentration to initial EHPA concentration was less than 0·1, the metals were extracted by the reaction:and a correlation for the equilibrium distribution coefficients was obtained from the thermodynamic equilibrium relationship for this reaction, taking into account metal ion complexing in the aqueous phase. Ammonium hydroxide and sodium hydroxide were used as alkalis for pH adjustment and similar distribution coefficients were obtained with both whenLwas less than 0·1. ForLgreater than 0·1, metal‐EHPA polymers were also formed in the organic phase, a typical step in their formation being:Equilibrium relationships were obtained from consideration of the equilibrium constants of the typical step and the reaction for monomer formation. The nature of the alkali used for pH adjustment influenced the distribution coefficients whenLexceeded 0·1, higher distribution coefficients being obtained with sodium hydroxide than with ammoni

ISSN:0021-8871    

DOI:10.1002/jctb.5010190403

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractKinetic studies of the transfer of copper and cobalt (separately) between aqueous solutions of their sulphates and organic phases consisting of solutions of di(2‐ethyl hexyl) phosphoric acid (EHPA) in kerosene were made by an ‘equilibrium extraction’ technique, in which radioactive isotopes of the metals were transferred between phases which were otherwise in equilibrium. The total resistance to mass transfer was found to be greater than that predicted from the mass‐transfer resistances of the aqueous and organic phases, the additional resistance to mass transfer being between 30 and 75% of the total resistance. When the concentration of free EHPA in the organic phase was greater than 0·01 g mole/l (which is approximately equivalent to a ratio of the metal concentration in the organic phase to the initial organic‐phase EHPA concentration of less than 0·25), expressions for these additional resistances were obtained from consideration of the kinetics of the extraction reaction, with a rate‐controlling step equivalent to the reaction of a metal ion with an EHPA dimer to form a metal‐EHPA compound and a hydrogen ion. At lower organic‐phase‐free EHPA concentrations, the additional resistances were lower and did not show any marked dependence on pH or reac

ISSN:0021-8871    

DOI:10.1002/jctb.5010190404

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractAn experimental investigation is presented of the foam separation of cyanide complexed with ferrous iron, using a cationic surfactant, ethylhexadecyldimethylammonium bromide. With a 25 min. foaming time, an initial iron to total cyanide ratio of 0·351:1 and an initial surfactant to complexed cyanide ratio of about 0·34:1 suspensions containing from 1·54 to 3·08 mM total cyanide can be reduced to about 0·11 mM in complexed cyanide and 0·29 mM in non‐complexed cyanide.The rate of surfactant removal was satisfied by a first‐order relationship, similar to that obtained with colloidal ferric oxide. The rate of complexed cyanide removal was satisfied by a reversible, approximately first‐order relationship eliminating the residual surfactant concentration. The pulsed addition of surfactant in three dosages during the course of an experiment, compared with a single dose at the beginning of an experiment, produced lower residual concentrations of complexed cyanide and higher foam volumes. At an iron to total cyanide ratio of 0·351:1,90% of the complexed cyanide concentration could be removed by one fifth less surfactant, using pulsed addition, compared with a

ISSN:0021-8871    

DOI:10.1002/jctb.5010190405

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

摘要:

AbstractThe kinetics of the pyrolysis of pureo‐,m‐ andp‐terphenyl and of material mixed with Attapulgus clay were studied. 10 to 12 times moreo‐,m‐ andp‐terphenyl was decomposed in the clay‐catalysed experiments and a strong isomerisation ofo‐ intom‐ andp‐, andm‐ intop‐terphenyl appeared. Twice as much benzene and biphenyl was formed, in the runs to which clay had been added. Similar differences were obtained for the quaterphenyl, triphenyl and triphenylbenzene formations. From the catalysed experiments 50 times as much total gas was found consisting of 41% hydrogen, 19% methane, 7% ethane, 2% propane, 1·5% n‐pentane, 3·8% isopentane, 2·5% ethylene, 0·4% acetylene, 0·9% propene and 32% butenes. The uncatalysed runs yielded 82% hydrogen, 4% methane, 1% ethane, 0·4% propane 0·2% n‐pentane, 0·3% isopentane, 10% ethylene, 2·8% acetylene, 1·2% propene and 2% butenes. It is suggested that the thermal decomposition of pure terphenyls follows a radical mechanism while the clay‐catalysed pyro

ISSN:0021-8871    

DOI:10.1002/jctb.5010190406

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY

ISSN:0021-8871    

DOI:10.1002/jctb.5010190408

出版商:John Wiley&Sons, Ltd    

年代:1969

数据来源: WILEY