Inorganic colloids

There were essentially three reasons for this opposition. Firstly, many macromolecular compounds in solution behave as colloids. Hence they were assumed to be identical with the then known inorganic colloids. This in turn implied that they were not macromolecular at all, but were actually composed of small molecules bound together by ill-defined secondary forces. Such thinking led the German chemist C. D. Harries to pursue the search for the rubber molecule in the early years of the twentieth century. He used various mild degradations of natural rubber, which he believed would destroy the colloidal character of the material and yield its constituent molecules, which were assumed to be fairly small. He was, of course, unsuccessful. 

This protocol was extended to other inorganic colloids (e.g., ZnS, PbS), and it was pointed out that such extension paves the way to an electrochemical coding technology for the simultaneous detection of multiple DNA targets based on nanocrystal tags with diverse redox potentials [148]. 

FIGURE 14.5 Multiprotein electrical detection protocol based on different inorganic colloid nanocrystal tracers, (a) Introduction of antibody-modified magnetic beads (b) binding of the antigens to the antibodies on the magnetic beads (c) capture of the nanocrystal-labeled secondary antibodies (d) dissolution of nanocrystals and electrochemical stripping detection (reproduced from [29] with permission). 

Nodwell, L. M. and Price, N. M. (2001). Direct use of inorganic colloidal iron by marine mixotrophic phytoplankton, Limnol. Oceanogr., 46, 765-777. 

Van Moorleghem C, Six L, Degryse F, Smolders E, Merckx R. Effect of organic P forms and P present in inorganic colloids on the determination of dissolved P in environmental samples by the diffusive gradient in thin films technique, ion chromatography, and colorimetry. Anal. Chem. 2011 83 5317-5323. 

The effect that hydrophobic organic substances can become sorbed to organic coatings can be used to make sorbents by coating inorganic colloids such as ferri-hydrite with surfactants. Such surfactant-coated surfaces contain films of hemicelles (see 4.5) which are able to remove hydrophobic solutes, such as toluene or chloro-hydrocarbons, from solution (Holsen, et al., 1991). 

Colloids are suspended particles in a solution medium and will not settle out over time. They are common in natural waters and can enhance the apparent solubility of a wide range of water pollutants, both organic and inorganic. Colloids maybe considered as an extension of the solid and aqueous phases and are formed by conditions that can be quite variable in time and space hence colloids can be dynamic. The composition of colloids can vary with the composition of the solid and aqueous phases. Colloids can be made up of organic, inorganic, or a mixture of materials. 

Inorganic colloids Sodium hydroxide, sodium dodecyl sulphate, sodium dodecyl benzene sulphonate... 

Colloids Organic Colloids Inorganic Colloids iron oxyhydroxides... 

Oh, S.J. Cook, D.C. Townsend, H.E. (1998) Characterization of iron oxides commonly formed as corrosion products on steel. Hyper-fine Interactions 112 59-65 Ohmori, M. Matijevic, E. (1992) Preparation and properties of uniform coated inorganic colloidal particles. VII. Silica on hematite. J. Colloid Interface Sci. 150 594-598 Ohta, S. Effendi, S. Tanaka, N. Miura S. (1993) Ultisols of lowland Dipterocarp forest in East Kalimantan, Indonesia. Soil Sci. Plant Nutr. 39 1-12... 

Farad. Boc. xiv. 10,1921) for the composition of the sols and gels of the inorganic colloidal hydroxides, e.g. zirconia produced by the hydrolysis of zirconium oxychloride. By electropotentiometric measurements of the hydrogen and chlorine ion concentrations of sols formed by hydrolysis as well as freezing point, conductivity and transport number determinations he has shown that a series of salts are formed of the types ... 

The influence of humic acid on the adsorption of europium onto inorganic colloids as a function of pH. Colloids Surfaces A Physicochemical and Engineering Aspects, 99, 187-199. 

If this treatment of forces between particles fails to convince the reader that it is natural for particles to stick together, one can resort to the more intuitive approach. It is well known that inorganic colloids require a stabihzing agent to prevent their sticking together and eventually precipitating, hi other words, precautions usually have to be taken to prevent the natural tendency of these particles eventually to stick to each other. 

Weiser HB (1933) Inorganic colloid chemistry, vol 1, The colloidal elements. Wiley, New York... 

The inorganic colloidal calcium phosphate associated with casein in normal milk dissolves on acidification of milk to pH 4.6 so that if sufficient time is allowed for solution, isoelectric casein is essentially free of calcium phosphate. In the laboratory, best results are obtained by acidifying skim milk to pH 4.6 at 2°C, holding for about 30 min and then warming to 30-35°C. The fine precipitate formed at 2°C allows time for the colloidal calcium phosphate to dissolve (Chapter 5). A moderately dilute acid (1 M) is preferred, since concentrated acid may cause localized coagulation. Acid production by a bacterial culture occurs slowly and allows time for colloidal calcium phosphate to dissolve. The casein is recovered by filtration or centrifugation and washed repeatedly with water to free the casein of lactose and salts. Thorough removal of lactose is essential since even traces of... 

References Friend, I, 78 Mellor, I, 768 Alexander, Colloid Chemistry, 4 vols. (1926-1932) Bancroft, Applied Colloid Chemistry (1926) > Bogue, Colloidal Behavior, 2 vols. (1924) Colloid Symposium Monographs, beginning 1923 Hatschek, Introduction to the Physics and Chemistry of Colloids (1922) Thomas, Colloid Chemistry (1934) Weiser, The Colloidal Salts, (1928) The Hydrous Oxides (1926) Inorganic Colloid Chemistry (1933). 

Table 1.1 shows the proportion of the several constituents found in the dissolved, diffusible state. Actually, phosphate is present in five classes of compounds inorganic dissolved, inorganic colloidal, water-soluble esters, ester-bound in caseins, and lipid. These can be determined by making the following analyses ... 

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