Complex colloid systems

Organosols, being complex colloidal systems, differ from solutions in that the individual resin particle is dispersed in the suspending liquid, but not dissolved. Formulations low in dispersant tend to agglomerate, are unstable on aging, and may... 

We may draw a close analogy here between the behaviour of colloidal dispersions and molecular systems. Thus the first case discussed above is analogous to the presence of clusters of molecules in a vapour approaching its condensation point, or in a solution close to saturation. The limiting concentration at which flocculation occurs corresponds to the saturation vapour pressure, or to the solubility of a solid in solution. More complex colloidal systems often exhibit phase behaviour which is paralleled by various phase separation phenomena in molecular systems. Detailed discussion ofthese matters is outside the scope of this book. However, pursuit of these analogies and their interpretation is a currently active area of research. 

Some of these conditions (and the list could be made longer) are very stringent, whereas others may appear as less essential, but no doubt the manufacturing and designing technologists must keep all of them in mind when sending a new formulation to the marketplace. In any case, this. set of conditions makes pharmaceutical suspensions very complex colloidal systems that can display interesting and intricate physical properties,. some of which are detailed in Chapter 4. 

Chapter X, entitled Complex Colloid systems, though for a greater part dealing with coacervates, also takes into consideration colloid systems of other kinds in which the ionised groups play a similar role. 

We might thus explain the low viscous character by the existence of so-called complex relations (see Chapter X Complex Colloid Systems) between the positive ionised groups of the macromolecule and the dissociated sulphate ions ... 

Complex coacervation is dealt with more extensively in the Chapter, Complex Colloid Systems , Ch. X p. 335. For a brief characterisation see however the right-hand column of the summary on p. 256. 

The need for investigating these reversal of charge phenomena with ions other than H or OH, originated from a study of the so-called complex colloid systems ", dealt with in the next chapter (Ch. X). As the results obtained have a more general character, they have been brought together in this chapter. 

In this Chapter we deviate from the division of the subject matter in this volume (II) of Colloid Science announced in Chapter I, 5, p. 13 according to the kind of phase or state of dispersion of a multiphase colloid system. The possibility of the production of complex colloid systems is not connected with one of these modes of occurrence but with the electrolytic nature of the colloid(s) in question. 

Under the term complex colloid systems are included colloid systems of all kinds, in which certain interactions, which we shall denote by complex relations between the ions (in a broad sense) composing them are present. This concept cannot be settled here in a few words but will already be outlined more distinctly in 2. 

It is possible therefore to subdivide the complex systems according to the latter principle of classification into various cases but it does not strike the essential point which is characteristic of complex systems and indeed produces no rational order in the mutually very varied behaviour of the complex colloid systems. 

The remaining 12 contain at least one colloid and thus form the real complex colloid systems. Only 6 of these (the underlined ones) have been realised and call for discussion in this chapter. 

Indeed in the field of the complex colloid systems it is just the characteristic charge elements of the colloid (equivalent weight, polarisability of the ionised groups) and of the ions (valency, radius, polarisability) which play a decisive role. It is for this reason that these charge elements were already discussed in detail in chapter IX (p. 259). 

---