Intermicellar liquid

A sol can be destabilized by increasing its temperature or by adding an electrolyte. A temperature increase reduces the quantity of intermicellar liquid by evaporation and increases the thermal agitation. This increases particle collisions... 

The consolidation mechanism of SPC compositions containing these additives can be considered as resulting from two processes decompression of silicon acid gel due to a decrease in the surface tension of intermicellar liquid and polymerization under the influence of acid solutions. 

Intermicellar Liquid An older term for the contiuous (external) phase in micellar dispersions. See also Continuous Phase, Micelle. 

In order for a silica sol to lower its specific surface free energy by particle growth or aggregation to form a sol of lower surface area, it is necessary to reverse the ionization and return the adsorbed ions to the intermicellar liquid. According to Yates the free energy change will be yS, where y is the value of the specific interfacial free energy between the sihca surface and water. The latter is a function of particle size and thus of S. 

It should also be noted that the possibility for a wide choice of hydrolytic polycondensation reaction parameters (nature, composition, and ratio of reacting components nature of a nonaqueous solvent amount of a hydrolyzing agent pH and temperature of a reaction medium nature of intermicellar liquid conditions of aging and drying of a gel etc.) allows one to exercise some control over properties of final products (in the first place over structure-adsorption characteristics of xerogels). 

How the charge of hydrophobic colloids comes into beit has been discussed in detail in Volume I of this book. In this discussion the idea came to the fore that the carriers of the chaise on the particles are in this case usually adsorbed ions. The degree of adsorption and with it the magnitude of the charge depends on the electrolyte concentration in the intermicellar liquid, in the first place on the concentration of the potential-determining ions and secondarily also on the concentration of the other (indifferent) electrolytes. 

In a lyophobic sol one distinguishes between the sol particles and the liquid in which they are embedded, called internal and external phase or micelles and intermicellar liquid respectively. Moreover, there is the interface between the two pliases, on which adsorption phenomena of the utmost importance for the stability of the colloid are present. 

Besides the particles themselves, the interface is the most interesting region of a sol. In order to be able to analyze the interface, ho vever, and to understand its beha-vioury knowledge of the composition of the intermicellar liquid is indispensable (cf... 

Because this adsorption may be present partially in the form of a diffuse double layer (thisCh 4 c p 78, Ch IV p 115) which may extend considerably into the solution phase, the notion of intermicellar liquid has to be defined more precisely. In a very dilute sol the composition of the liquid far away from every sol particle may be considered to be tliat of the intermicellar liquid In more concentrated systems the best definition is the liquid with which the sol can be in equilibrium when the sol particles are prevented from diffusing into it ... 

The most correct way to prepare the intermicellar liquid is therefore a dialysis without renewal of the external liquid until eqitilibrium between sol and external liquid is obtained This equilibrium liquid is then identi l with the intermicellar liquid ... 

If the sol particles are large and/or heavy, they may sediment rapidly enough to leave a clear layer of intermicellar liquid on top in a reasonable time ... 

Pauli has often used the supernatant of an elcctrodecantation as the intermicellar liquid I his procedure is certainly not permissible, because in electrodecantation not only the sol particles but also the ions are decanted thus simulating an intermicellar liquid which is too dilute ... 

A property of the electrical double layer which is of very great practical importance, is the possibility of exchange of ions in the outer layer against other ions present in the intermicellar liquid This process of ion exchange that can be studied in a very pure form in colloids (chapter IV, 9, p 175) finds applications on a very large scale in nature, in the ionic balance of the soil, and in industry (see chapter IV, 9 d, p 183) ... 

Flocculation is usually brought about by the addition of electrolytes to a sol. In 4 c, p. 78, it has been mentioned that the electric properties (charge, electrophoresis) of sol particles are strongly dependent upon the electrolyte content of the intermicellar liquid, and now we find the same for the stability. It is therefore obvious to look for a direct relation between charge and stability. 

Fundamentally the difficulty is this what is the pH (or px) of a sol Is it the pH of the intermicellar liquid or should it be understood as a property of the suspension as a whole A simple experiment shows that two different results of the pH determination are possible. If a sol or suspension is in equilibrium with a particle-free solution... 

Van Os used the difference in mobility between the ions in the double layer and the ions in the intermicellar liquid " to measure the exchange of ions by conductometry. He ""titrated"" an (AgI)FH+-soI with barium nitrate. The H+-ions were exchanged against the added barium ions. This caused an increase of the mobility of H -ions and a decrease for the Ba -ions. Because of the much larger mobility of the H+-ions the total effect of exchange is an increase in conductivity which could be measured, and which served as a means of evaluating the exchange quantitatively. 

In several hydrophobic sols, especially those with flat or elongated particles it is possible to induce gelation by the addition of an amounf of electrolyte not quite sufficient to lead to a normal flocculation. Evidently the partly discharged particles arc attached to each other at a very few spots, still repelling each other on the main part of their surface and thus forming a network which immobilisies the included intermicellar liquid. 

Many gels, especially thixotropic ones with a low content of dispersed matter, contract in the long run with liberation of a part of the intermicellar liquid This phenomenon is called syneresis and is easily explained by the fundamental instability of gels, at least of the lyophobic type The system, in gelling, has only formed a relatively small number of contact places and by forming a greater number of contacts, which inevitably entails a contraction of the dispersed phase (see Fig 12), the free... 

In the left part of eq. (2) the first component expresses the liquid consumption for sorption and chemical interaction with aluminium hydroxide particles, the second component - for creation of equilibrium concentration of peptizator in intermicellar liquid. 

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