The smaller the size of an ion, the more will be its polarising power. Similarly, for negatively chargedsol like as 2 s 3 the cations cause coagulation. In order to explain the schuzehardy rule, you have to take into account that you are working with a colloidal dispersions stabilized electrostatically. Here the schulze hardy rule is expanded to much smaller, nano. An expansion of schulze hardy rule and hofmeister series to nanometer. They have explained that the ccc is controlled by the counterion concentration. This dependence is established by means of measurements of the stability ratio for. Shifts of the critical coagulation concentration ccc in particle suspensions in salt solutions containing multivalent coions and monovalent counterions are rationalized. A reassessment of the applicability of the dlvo theory as an explanation for the schulze hardy rule for colloid.
Aluminum and ferric based salts meet these criteria and are almost universally used. Part i the ions of electrolyte having opposite charge with respect to as that of the sol particles are responsible for the coagulation. One of the first surprising generalizations regarding colloid stability 18801900 was that the critical electrolyte concentration required to flocculate cfc a variety of positive and negative colloids decreased as z. Cations in macroionic solutions follows the classical cationic hofmeister series. Nature volume 190, pages6896901961cite this article. Hardy rule, which applies in the case of multivalent counterions, and states that the ccc is inversely proportional to the sixth power of the valence. A naive explanation of the inverse schulze hardy rule would come from the original argument of schulze and hardy.
It depends upon the valency of the active ion are c. Coagulation by multivalent counterions and the schulze. Specifically, it can be shown that the critical coagulation concentration is inversely proportional to the coion valence. This video explains very important topic from the chapter surface chemistry.
Hofmeister schulze hardy rule coarsegrained model saxs introduction. On the basis of hardy schluze rule,explain why the. The effective ions of the electrolyte in bringing about coagulation are those which carry charge opposite to that of the colloidal particles. One observes that the ccc is inversely proportional to the valence, and this behavior is referred to as the inverse schulze hardy rule. The coagulation capacity of different electrolytes is different. Arrange following in the order of coagulating power for al2o3 naci, cacl2, alci. The commonly presented derivation of this rule assumes symmetric electrolytes and highly charged particles. It depends upon the valency of the active ion are called flocculating ion, which is the ion carrying charge opposite to the charge on the colloidal particles. Rediscovering the schulze hardy rule in competitive.
Greater is the valency of coagulating ion added, the greater is its power to cause precipitation. Expanding the schulzehardy rule and the hofmeister series to. Application of the schulzehardy rule to haematite and. This rule describes an interesting situation of the aggregation of charged colloidal particles in the presence of the multivalent coions. Hardy schulze rule,protective colloid, gold number online chemistry tutorial iit, cbse chemistry, icse chemistry, engineering and medical chemistry entrance exams, chemistry viva, chemistry job interviews. The inverse schulzehardy rule was recently proposed based on experimental observations cao et al. This rule is addressed theoretically and confronted with recent experimental results. On the other hand, the inverse schulze hardy rule was only given as an empirical dependence based on experimental observations. Pac, 1972, 31, 577 manual of symbols and terminology for physicochemical. This rule describes an interesting new situation of the. It means that coagulation power of an electrolyte is directly proportional to the fourth power of the valency of the effective ion i. This observation is often referred to as the hardy schulze law.
Aggregation behavior of aqueous cellulose nanocrystals. T1 rediscovering the schulzehardy rule in competitive adsorption to an airwater interface. The schulze hardy rule suggests a strong dependence of the critical coagulation concentration ccc on the ionic valence. Particle aggregation is a widespread phenomenon, which spontaneously occurs in nature but is also widely explored in manufacturing. Schulze hardy rule the generalization that the critical coagulation concentration for a typical lyophobic sol is extremely sensitive to the valence of the counterions high valence gives a low. Aggregation of colloidal particles in the presence of. Rediscovering the schulzehardy rule in competitive. Expanding the schulzehardy rule and the hofmeister series. It stems from the end of the nineteenth century, and its qualitative validity has since been confirmed over and again for a variety of. An extension of the schulzehardy rule to asymmetric electrolytes. Schultzhardy rule article about schultzhardy rule by. Greater the charge on flocculating ion and smaller is the amount of electrolyte required for precipitation, higher is the coagulating power of coagulating ion hardy schulze lclw. Macroions with increased surface charge density follow the schulze hardy rule with an increased exponent. According to the schulzehardy rule, known since about.
Influence of valency of ion on aggregation of lyophobic particle can be correlated to zeta potential and sedimentation volume hofmeister of lyotropic rule apply to hydrophilic. The schulze hardy rule is an empirical realization of these property. The coagulation power of precipitated ion is more if its valency is high. Phosphate ion bear 3 charge while chloride ion carries only 1 charge and due to high charge. The sensitivity of lyophobic colloids to coagulating electrolytes is governed by the charge of the ion opposite that of the colloid, and the sensitivity. International conference on surface and colloid science, international conference on surface and colloid science, icscs, surface and colloid science, third, stockholm, sweden, 1979082019790825. The applicability of the schulze hardy rule to haematite and haematitehumate mixtures has been investigated by measuring the rate of fast and slow coagulation after the addition of increasing concentrations of mono, di and trivalent ions. The schulze hardy rule 1 and the low charge dh limit 3 were both derived theoretically. Schulze hardy rule this rule is valid only for system in which there is no interaction between electrolyte and ion of double layer of particle surface. Request pdf expanding the schulzehardy rule and the hofmeister series to nanometerscaled hydrophilic macroions the. Schulze hardy rule form insoluble precipitates in water for adsorption and sedimentation. The required amount of electrolyte for the coagulation of a definite quantity of colloidal solution is dependent on the valency of the coagulating ion which is the ion that holds a charge which is opposite to the charge of the colloidal particles. Rediscovering the schulzehardy rule in competitive adsorption to an airwater interface.
A simple and inexpensive experiment for verifying the schulze hardy rule. Greater is the valency of the coagulating or the flocculating ion, greater is its power to bring about the coagulation. Hardy schultz rule the coagulation of a colloidal solution by an electrolyte does not take place until the added electrolyte has certain minimum concentration in the solution. This law takes into consideration only the charge carried by an ion, not its size. The schulze hardy sh rule is an empirical rule, stating that the coagulation concentration c cr of hydrophobic sols decreases very strongly with the valency z of the counterion. Schulze hardy rule the generalization that the critical coagulation concentration for a typical lyophobic sol is extremely sensitive to the valence of the counterions high valence gives a low critical coagulation concentration. Thus, an increase in the ionic strength is results in a smaller debye length, more compacted double layer and a smaller barrier to aggregation. According to hardy schulze rule, greater the valency of the active ion or flocculating ion, greater will be its coagulating power. Hardy schulze rule,protective colloid, gold number.
Rediscovering the schulzehardy rule in competitive adsorption to. Derivation of the inverse schulzehardy rule nasaads. Rediscovering the schulze hardy rule in competitive adsorption to an airwater interface patrick c. Introduction more than a century ago, schulze and hardy discovered that. Yeah hardy schulze rule does say that for a positive sol as the charge of the anion in the salt increases the flocculating value decreasesif the charges of anions in 2 salts are different then does not depend on number of negative ions per molecule of salt and the rule still holds good. It depends upon the valency of the active ion are called flocculating ion, which is the ion carrying charge opposite to the charge of the colloidal particles. Notice that for the same concentrations of ions, the ionic strength increases with the square of the ion charge. The schulzehardy rule for the determination of the critical coagulation concentration ccc of counterions is examined for the case of an asymmetric electrolyte.
Derivation of the inverse schulzehardy rule request pdf. For positively charged sol like feoh 3, the anions cause coagulation. This states that the ion that causes a soluble to coagulate is opposite in sign to the electric charge of the colloidal particle. The above relation, named the schulzehardy rule, is valid for highly charged particles.
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