Hardy’s rule

The role of sodium ions is predicted to be small according to Schulze-Hardy s rule that is, the effectiveness of counterions in the interfacial phenomena is approximately proportional to the sixth power of the counterion charge. The formation of complexes between Na+-ions and anionic sites on the montmorillonite surface is included here for the sake of completeness, although such complexes are subject to reservations because they are unknown in aqueous solutions, and evidence against their physical reality has been presented (Janssen and Stein 1986). Indeed, as will be seen later, they are not prevalent. 

Some interesting conclusions may be drawn from a consideration of the magnitude of the interfacial surface tensions of various liquids. The significance of these was first pointed out by Hardy Froc. Roy. Soc. A, Lxxxviii. 303, 1913) and emphasised by Harkins J.A.G.S. XXXVIII. 228,1916 xlil 700,1920). We have noted that Antonow s rule only applies to mutually saturated solutions. If two... 

Schulze-Hardy rule.1 Specific properties of the ions promoting easy adsorption are also important e.g. with a series of sodium salts of aromatic sulphonic acids, the introduction of an aliphatic side chain decreases the concentration necessary to diminish the potential by a given amount, by a factor of three for each additional CH2 group in the side chain2 this is another case of Traube s rule in adsorption. 

Schrock alkylidyne catalysts, 26 948-949 Schrodinger s equation, 16 734-735 Schultz-Flory distribution, 20 156 Schultz-Flory equation, 17 714 Schulze—Hardy rule, 7 289, 10 121 Schweizer, M. E., 11 248 Schwenzfeier process, 3 641 Science... 

In the following years important research centers formed at several universities. In Exeter. N.C. Rydon (Plate 36) and his students, e.g. D. Jarvis, carried out fundamental studies on the rules governing cyclization via disulfide formation and on blocking groups that can be removed via base catalyzed jS-elimination. The Exeter school was the starting point of the career of several distinguished peptide chemists, for instance of P.M. Hardy and B. Ridge. Some of Rydon s... 

The introduction of several refinements was necessary to explain various details. The quantitatieve agreement between theory and experiment, and the deviations from the rule of Schulze and Hardy (lyotropic effects) made it necessary to reckon explicitly with dimensions and the specific adsorbality of the ions. To this end. Stern s theory has been introduced. 

The hydrogen and hydroxide ions are especially effective in determining the nature of the charge. Hardy t found that albumin had no perceptible charge in pure water, but that traces of alkalies or acids caused the albumin to go to the anode or to the cathode respectively. Perrin t found the same rule to hold for many suspended powders, and many hydrosols, such as albumin solutions. Pauli corroborated Perrin s results on proteids. 

Hardy, M., AgostineUi, S. (2008). Organisation as a multi-dimensional network of communicative actants mediated and organised by an organising network of cultural rules. In Proceedings, Materiahty, Agency and Discourse, Montreal. 

The most striking facts to be explained by a theory on the stability of hydrophobic colloids are the valency rule of Schulze and Hardy (see chapter II, 5 c, 1, p 81) and a certain relation between the stability and the -potential. Hardy already observed that a sol flocculates when it is nearly isoelectric with its surroundings, that is when the -potential is reduced to zero. Later investigations by Powis introduced the concept of a critical s-potential below which a sol flocculates and above which it is stable. This critical potential was found to be about 25-30 milli-vplts. The extension of the experimental material on one hand and the criticisms rised against the interpretation of electrophoresis measurements (see chapter V, 6b, p. 210) on the other, made the existence of a critical potential doubtful. Other quantities, connected with the electrolytic character of hydrophobic systems, have been proposed as governing the stability. Of these we mention the function introduced by Eilers and Korff and the activity coefficient / introduced by Wo. Ostwald In the theory of Verwey and Overbeek which will be set out in the next sections, the role of the -poten- tiai is less conspicuous although the electrical double layer remains of fundamental importance. 

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