Double valency rule coacervation

Fig. 11. Double valency rule in the suppression of complex coacervation of 0.01% gelatin and...

Fig. 12 gives similar results with the so-called coacervate volume method. In contrast to the viscosimetric or turbidity method this is a direct method. It is serviceable in sufficiently concentrated colloid mixtures. In it one reads off directly the volume of the separated coacervate in a graduated tube (after sedimentation and coalescence to a homogeneous liquid column). Here also we see that added salts suppress coacerv-ation and that the double valency rule holds. 

If one regards the complex coacervate as a sightly soluble compound of polyvalent colloid ions, one can understand the occurrence of the double valency rule as increase of solubility as a result of the shielding of the colloid cations by the anions of the added salt and of the colloid anions by the cations of the added salt. 

If now one investigates the influence of salts of the same valency types as occur in the " double valency rule , the curves for these salts are seen to form a fan in which the salts are always arranged in the same sequence Fig. 14 gives an example for a positively charged coacervate system, but the sequence is the same for an uncharged or a negatively charged system. This is as follows ... 

Only at higher salt concentrations the suppression then (after possibly also passit through a stage of readily visible coacervate drops) proceeds in the usual way accordiiig to the double valency rule. 

Furthermore added indifferent salts suppress the coacervation whereby the so-called double valency rule (see p. 350) again appears ... 

---