Highly dispersed colloid

Preparation of stabilized highly dispersed colloidal platinum, that is, Pt particles of from 1 to 10 nm size in aqueous solution by chemical reduction followed by adsorptive precipitation of the dispersed Pt particles on the outer and inner surface of soot particles. 

Metal Species in the Form of Highly Dispersed Colloids... 

Highly dispersed colloids (Morrison 1989 Mota and Simaes-Goncalves 1996), such as (FeO)OH, Fe(OH)3, Mn02, AgjS, CujS. 

Only the "amorphous flocculation of corpuscular proteins could still be represented by Fig. 7 in so far as the separated highly dispersed colloid-rich phase is not microcrystalline or paracrystalline, if at any rate one replaces the very great hydration by a suitably smaller one, similarly the spheres by appropriately shaped corpuscles and thinks of these as placed in the "coacervate at short distances from each other but in such a way that there is still no question of a rigorous order... 

In an interesting example of radiolytic colloid synthesis, both the colloidal metal and the polymer are produced simultaneously by radiolysis of the solutions of a metal salt and a monomer. Radiolysis of aqueous solutions of H2PtO containing either acrylamide or A/-methylolacrylamide with a CO y-radiation source yielded highly dispersed colloidal platinum (diameter 1.7 nm). [104]... 

In reserving judgement on the nature of these dusters, their importance should not be underestimated. The physics and diemistry of small metal aggregates is under intense scrutiny, and these materials provide a unique access into this area, regardless of whether we conader them as giant molecules or extremely highly dispersed colloidal dusters. [181]... 

When potassium thiocyanate (m.p. 173-179 C) is heated to about 430 C, the molten mass turns blue after cooling the color disappears. This phenomenon is probably due to the splitting-off of sulphur, which remains in highly dispersed colloidal form in the molten potassium thiocyanate, and which regenerates potassium thiocyanate on cooling ... 

With foams, one is dealing with a gaseous state or phase of matter in a highly dispersed condition. There is a definite relationship between the practical application of foams and colloidal chemistry. Bancroft (4) states that adopting the very flexible definition that a phase is colloidal when it is sufficiently finely divided, colloid chemistry is the chemistry of bubbles, drops, grains, filaments, and films, because in each of these cases at least one dimension of the phase is very small. This is not a truly scientific classification because a bubble has a film round it, and a film may be considered as made up of coalescing drops or grains. ... 

The electrokinetic processes can actually be observed only when one of the phases is highly disperse (i.e., with electrolyte in the fine capillaries of a porous solid in the cases of electroosmosis and streaming potentials), with finely divided particles in the cases of electrophoresis and sedimentation potentials (we are concerned here with degrees of dispersion where the particles retain the properties of an individual phase, not of particles molecularly dispersed, such as individual molecules or ions). These processes are of great importance in particular for colloidal systems. 

In order to deposit gold on the supports with high dispersion as nanoparticles (NPs) and clusters, there are at least nine techniques which can be classified into five categories well mixed precursors, specific surface interaction, mixing gold colloids [18], physical deposition [19,20], and direct reduction [21]. The former two categories are schematically presented in Figure 3. 

Among the various branches in colloid and interface science, polymer adsorption and its effect on the colloid stability is one of the most crucial problems. Polymer molecules are increasingly used as stabilizers in many industrial preparations, where stability is needed at a high dispersed phase volume fraction, at a high electrolyte concentration, as well as under extreme temperature and flow velocity conditions. 

Wieringa, J.A. Dieren, F. van Janssen, J.J.M. Agterof, W.G.M., 1996, Droplet breakup mechanisms during emulsification in colloid mills at high dispersed phase volume fraction, Chemical Engineering Research Design, 74, 554-562. 

H. Bonnemann, W. Brijoux, R. Brinkmann, E. Dinjus, T. Jouben, R. Fretzen, and B. Korall, Highly dispersed metal clusters and colloids for the preparation of active liquid-phase hydrogenation catalysts, J. Mol. Catal. 74,323-333 (1992). 

When superheated selenium vapour is passed into air-free water, colloidal solutions are formed which are usually rose-coloured, but at first of a blue tint and cloudy. Under the most favourable conditions clear yellowish-red or deep red sols may be obtained,4 the former being the more highly dispersed. The blue sols after dialysis are extremely stable, but non-dialysed sols decompose after a few days, selenious acid being detected except in the yellowish-red sols. The dialysed sols may be frozen to an almost colourless ice which at the ordinary temperature thaws and decomposes. The sols are negative and are readily coagulated by the addition of chlorides. 

Colloidal arsenious oxide may be obtained in a highly dispersed condition by the vaporisation of arsenic in the electric arc and oxidation of the fume in a current of air.11 The size of the particles thus obtainable corresponds with the upper limit of the colloidal state (100 ftp.). 

From solutions of pure arsenic acid the pentasulphide separates in a highly disperse form which adsorbs arsenic acid so strongly that the last traces of the latter react with great difficultv at the ordinarv temperature,6 although this is not the case at AO" C. In the presence of salts of multivalent cations which by hydrolysis yield colloidal hydroxides, the arsenic pentasulphide is flocculated, but the completion of the reaction is greatly delayed owing to adsorption of the arsenic acid, especially at low temperatures. 

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