Colloidal products

A less specific type of adsorption can sometimes be used if the required product forms insoluble hydroxides but the target element does not. In this case, the solution is made alkaline, and the carrier-free radio-colloidal product is readily absorbed on to filter paper in good yield, when, after washing, it can subsequently be dissolved in acid. This has been used for the separation of magnesium from aluminium, scandium from calcium and for several other elements (17), (26), (42), (44), (66), (103), (104), (105), (106). 

The methods used to prepare monodisperse colloids aim to achieve a large number of critical nuclei in a short interval of time. This induces all equally sized nuclei to grow simultaneously, thus producing a monodisperse colloidal product. 

Production of well-defined colloidal products Stability criteria of colloidal products Disability criteria... 

The mechanism of colloid production by means of these immersed... 

Upon addition of water, the hydration reactions initiate, and the hydraulic cement begins to gain strength. This process is very complex, but the strengthening effect is due basically to the formation of three types of hydration products colloidal products such as C2S xH20, which have a size of less than 0.1 p.m submicrocrystalline products such as Ca(OH)2, Al +, Fe +, and S04 phases with sizes from 0.1 to 1 tim and microcrystalline products, primarily of Ca(OH)2, with particle sizes greater than 1 p,m. The most common type of hydraulic cement, Portland cement, usually contains mostly colloidal products. 

To prepare solids using the sol-gel method, a sol of reactants is first prepared in a suitable liquid. Sol preparation can be either simply the dispersal of an insoluble solid or addition of a precursor which reacts with the solvent to form a colloidal product. A typical example of the first is the dispersal of oxides or hydroxides in water with the pH adjusted so that the solid particles remain in suspension rather than precipitate out. A typical example of the second method is the addition of metal alkoxides to water the alkoxides are hydrolysed giving the oxide as a colloidal product. 

In general terms these problems are not unlike those encountered in the manufacture of other colloidal products such as paints, face creams, and printing inks and toners, for example. The difference, of course, is that the inks and toners are hardly appetizing and one seldom cares about how they taste (Of course, physical stability alone does not determine the taste or the worthiness of a food product. Chemical reactions play a role in taste and in determining the structure, and other considerations such as nutritional value and esthetic appeal may also apply.)... 

FMC (1991). Marine colloids products balance taste, texture and mouthfeel in reduced fat foods. The Carrageenan People (FMC Corp.) 8. 

When stannous chloride is added to solutions of platinum salts a red coloration is produced, which is due to the formation of so-called red colloidal platinum, which is kept in a fine state of division by the colloidal products of hydrolysis of the stannous chloride.7 In the absence of a protective colloid the red platinum changes to brown colloidal platinum. An interesting analogy may be traced between this red. colloidal metal and the better-known colloidal gold, termed purple of Cassius. ... 

It should be apparent by now that miniemulsion polymerization systems have some properties that ought to be exploitable when making polymer colloidal products with unique or improved properties. This section will discuss some of these documented and potential applications. 

Cibaphasol [Novartis], TM for coacervate-forming colloidal product used in textile dyeing. 

Investigations into the possibilities for the formulation of the drug substance as a more complex drug delivery system such as an emulsion, liposomal, micro- or nanoparticle, or other colloidal product. 

The colloids, in particular albumin, are expensive solutions. Therefore, it is difficult to justify the additional cost of colloidal products unless the benefit-to-risk ratio is substantially greater than that associated with inexpensive crystalloid solutions. This does not appear to be the case based on randomized, controlled studies and meta-analyses comparing colloid and crystalloid solutions for acute circulatory insufficiency. Because other colloids, such as hetastarch, almost always have been compared with albumin and not with crystalloid solutions in published clinical studies (with no clinically important differences being found), there is no reason to suspect that these other colloids have any unique advantages as volume expanders. Adverse effects associated with colloids appear to be uncommon and generally are extensions of their pharmacologic activity (Table 24—4), but this is also true of crystalloids. The benefit-to-risk ratio appears to be similar for colloids and crystalloids thus, based on cost, crystalloids are preferred for initial treatment of circulatory insufficiency. 

The yellow NiCOa forms under the same conditions as the green, but at a temperature of 180°C and from very cone, solutions (0.22 moles of NiCla in 25 ml. of water and 0.38 moles of NaHCOa in 100 ml. of water). The yield is poor. At lower temperatures only colloidal products are obtained at temperatures between 180° and 250°C a mixture of 1 and II is produced. 

The kinetics of nanoparticle formation reaction, size and size distribution of the colloidal product solution depend strongly on the rate of nucleation and particle growth and the concentration dependence of both rates. Homogeneous particle sizes (narrow size distribution) are expected, if three conditions are fulfilled ... 

Two- and three-step arrangements of micromixers are also of interest for the generation of nanopartides of binary and complex composition. They can be realized for continuous flow processes and for segmented flow applications (Figure 17.10). The order of reactant application, the flow rates and flow rate ratios determine the properties of the colloidal product solution obtained. Strong dependences of the... 

Figure 17.11 Flow rate dependence of optical spectra of colloidal product solutions obtained by a flow-through two-step synthesis of Au/Ag nanoparticles (constant ratio of reactants).

Since both of the yellow silicomolybdic acids have only low intensity colours, several methods have been developed in which the complexes are reduced to intensely coloured blue complexes. These heteropoly acids are well-defined soluble compounds and not colloidal products as are the blue phospho- and arsenomolybdic complexes. The most conunon reducing agents are metol (p-methylaminophenol sulphate) and sulphite Strickland and Parsons, 1968), and ascorbic acid Koroleff, 1971). The manual method and flow-anal5rsis described below use ascorbic acid as the reductant. 

Another very important physical parameter one must consider is the size distribution of the colloids. A system consisting of particles of same size is called monodisperse. A system with different sizes is called polydisperse. It is also obvious that monodispersed systems will exhibit different properties compared to poly dispersed. In many industrial applications such as coating of substances in colloid form on tapes, as used for recording music (coatings on CD or DVD), the size of particles is an important characteristic. The methods used to prepare monodisperse colloids is to achieve a large number of critical nuclei in a short interval of time. This induces all equally sized nuclei to grow simultaneously and thus produces a monodisperse colloidal product. 

Polyelectrolytes are finding wide application in water purification treatments and also as thickeners in colloidal products (1). The level of surface activity in polyelectrolyte solutions is, however, usually so low that they are of little use as colloidal stabilizers. Some application of non-ionic polymers containing strongly polar groups, e.g. polyacrylamides, has been made in the field of stabilization, but their position is defensive economically and also from the standpoint of control of their stabilizing effects. 

We often use the term surfaces if one of the phases is a gas and the term interface between liquid-liquid, liquid-solid and solid-solid phases. All of these interfaces are important in colloid and surface science, in the understanding, manufacturing or in the application of colloidal products. However, there are many applications in surface science which are not directly related to colloids. 

Which analysis techniques would you use to characterize the following colloidal products paint, ice cream, shampoo, and lipstick ... 

Figure 1 Row through polymerisation cell for colloid production.

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