Of Ostwald

At equilibrium, crystal growth and dissolving rates become equal, and the process of Ostwald ripening may now appear, in which the larger crystals grow at the expense of the smaller ones. The kinetics of the process has been studied (see Ref. 103). 

An illuminating example is the effect of Ostwald ripening on pore size distribution in a sintered body, resulting from vacancy transfer from the smaller to the larger pores, where the decrease in the number and die increase in average diameter of the pores can be clearly seen. The disnibutioii curve for... 

If the pore size distribution is finally the result of Ostwald ripening, it follows that Di oc... 

Nine years later, the Zeitschrift fur physikalische Chemie was followed by the Journal of Physical Chemistry, founded in the USA by Wilder Bancroft (1867-1953), one of Ostwald s American students. The chequered career of this journal is instructively analysed by both Laidler (1993) and Servos (1990). Bancroft (who spent more than half a century at Cornell University) seems to have been a difficult man, with an eccentric sense of humour thus at a Ph.D. oral examination he asked the candidate What in water puts out fires , and after rejecting some of the answers the student gave with increasing desperation, Bancroft revealed that the right answer was a fireboat . Any scientific author will recognize that this is not the ideal way for a journal editor to behave, let alone an examiner. There is no space here to go into the vagaries of Bancroft s personality (Laidler can be consulted about this), but... 

S. Olive, U. Grafe, I. Steinbach. The modelling of Ostwald-ripening during non-isothermal heat treatments resulting in temperature dependent matrix solubihty of the precipitate forming elements a further development of the LSW-theory. Comput Mater Sci 7. 94, 1996. 

Somewhat in advance of the widespread usage of the colloidal connotation of Ostwald and others, investigators in a number of instances seem to have favored the view that cellulose, starch, rubber, etc., are polymeric, the term being used in much the same sense as it is used today. The idea that proteins and carbohydrates are polymeric goes back at least to Hlasiwetz and Habermann, who, in 1871, considered... 

According to the early view of Ostwald, acid-base indicators are weak acids or bases, the undissociated form of which differs in colour from the ionic form. For example, the molecule of an indicator HI dissociates in water according to the equation... 

These relations are used in the precise form of Ostwald s dilution law (2.4.17). 

Capillary viscometers that have this design are called Ostwald viscometers. There are many specific designs of Ostwald viscometers. The most frequently used are the Cannon-Fenske viscometer... 

Noyes himself had been a student of Ostwald. Lewis had spent the academic year 190001 at the institutes of Ostwald and Nernst. Colloquium topics at MIT in the period from roughly 1905 to 1910 included both chemical and physical topics Alfred Werner s coordination theory of valence, tautomerism, and the absolute size of atoms. 

Pt particle coalescence is due to migration. This mechanism is supported by observations that, upon cycling, Pt particle size distributions are shifted toward larger sizes, indicating that smaller particles are more mobile. It is noted that this observation could also result from the effects of Ostwald ripening. 

A.S. Kabalnov, A.V Pertzov, and E.D. Shchukin Ostwald Ripening in Emulsions 1. Direct Observations of Ostwald Ripening in Emulsions. J. Colloid Interface Sci. 118, 590 (1987). 

Y. Enomoto, K. Kawasaki, and M. Tokuyama Computer Modelling of Ostwald Ripening. Acta Metall. 35, 907 (1987). 

These three types of [L]-control maps strikingly remind us of the important role of Ostwald s dilution law in homogeneous catalysis. 

Case III (selectivity y = Pi/ pj = f (1L]o/[M]o) l]o = const.) is realized in open reactors where the catalyst is used right from the beginning and substrate as well as the controlling ligand are permanently delivered at a constant ratio. This sometimes is the best strategy to overcome the influence of Ostwald s dilution law in catalysis, but - as Scheme 3.3-4. indicates - fails below a critical ((L1o/IM1o)(l1o = const, ratio-... 

The definite integral may be evaluated if a does not exceed 0 1 by means of Ostwald s dilution law a c=K. For dlogc=-2[Pg.48]

Figure 2.9. The importance of dynamic (in situ) ETEM studies (a) Cu/C catalyst (particles are, e.g., at B) reacting at 200°C in 10% He/He gas after 30 min (b) time-resolved studies of the growth of catalyst particles (e.g. at B) indicative of Ostwald ripening, after 45 min (c) static studies of the same sample (the sample is cooled to room temperature and the gas is turned off) the image is not the same as in the dynamic studies in (b)—particles (e.g. at B) have moved (have faint contrast around them) and more features are present.

Unlike the results calculated for degrees of ionization from the depressions of the f.p., the values of Ostwald s constant computed from the electric conductivities of soln. of rubidium nitrate show marked deviations from constancy and they are thus constant with results with other strong electrolytes—the rubidium ion Rb and the N0V4on are among those with the greatest electro-affinities. The electrical conductivity of lithium nitrate is greater in methyl alcohdl than in water, but in... 

Taking into consideration both the work of Ostwald, and that of Papkov, extended investigations into the ability of solvents to dissolve esters and ethers of cellulose have been carried out by Moll [53] who has linked the results of his experiments both with the electrostatic constants and with surface tension. The results of Moll s... 

A.D. Brailsford and P. Wynblatt. The dependence of Ostwald ripening kinetics on particle volume fraction. Acta Metall., 27(3) 489—497, 1979. 

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