Contribution to the Physical Chemistry of Hevea Latex. II. Adsorption of Metallic Cations on the Surface of Latex Particles. Distribution of Alkali Metals, Alkaline Earth Metals, and Iron between the Two Phases of Latex Preserved with Ammonia

1952 ◽  
Vol 25 (1) ◽  
pp. 132-139 ◽  
Author(s):  
Robert Belmas
Keyword(s):  
Alkali Metals ◽  
Alkaline Earth ◽  
Organic Anion ◽  
Complex Structure ◽  
Living Organism ◽  
Alkaline Earth Metals ◽  
Adsorption Equilibria ◽  
Negative Surface ◽  
Metallic Cations ◽  
Two Phases

Abstract The study of latex is characterized by the fact that it is always difficult to draw any definite conclusions. One is confronted with a substance which has been synthesized by a living organism, and whose extremely complex structure is very different from that of the sols currently studied by colloid chemistry. However, ultracentrifugation makes it possible to obtain reliable results as far as partition of the natural metallic components between the dispersing and dispersed phases is concerned. The existence of equilibria of adsorption as a function of the dilution of latex and comparison of the experimental curves with the isotherms of Freundlich and of Langmuir shows that, in the case of latex, adsorption is not a simple phenomenon. At least two different processes seem to be involved: (1) electrosorption of the metallic cations by the negative surface of the rubber particles, and (2) indirect adsorption, whereby the metal is bound in a slightly dissociable form to an organic anion which is itself strongly adsorbed. This would explain the much weaker adsorption of the alkali metals, which possess only a positive charge, and whose salts are in general more easily dissociated than those of the alkaline earth metals. The results obtained for metals added to latex in the form of soluble salts lead to the same conclusions. Measurement of the adsorption equilibria for samples of latex containing different concentrations of rubber show that, the smaller the proportion of dispersing phase to dispersed phase, the higher is the adsoprtion. This phenomenon, which is evident with alkali metals as well as with alkaline earth metals, can be explained by the increase of the charge on the particles when the latex is diluted. An examination of the critical adsorption values for the different metals studied confirms the fact that the behavior of latex with salts is that of a mixed sol with both lyophilic and lyophobic properties. These results would be more valuable if confirmed and determined more precisely by an electrokinetic study. The determination of the potential of the particles by measuring the cataphoretic velocity with respect to the adsorption of metal ions would surely permit a more accurate interpretation of the mechanism of this adsorption.

scholarly journals Interactions Between Zinc Oxide and Alkali Metals, Alkaline Earth Metals and Halogens: A Theoretical Study

2017 ◽  
Vol 29 (3) ◽  
pp. 585-588
Author(s):  
Aned de Leon ◽  
Grace Jouanne-Jeraissati ◽  
Agustín Martínez-Contreras
Keyword(s):  
Zinc Oxide ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Theoretical Study ◽  
Alkaline Earth Metals

The Use of Some Ion-Exchange Sorbing Tracer Cations in Insitu Experiments in High Saline Groundwaters

1994 ◽  
Vol 353 ◽  
Author(s):  
J. Byegård ◽  
G. Skarnemark ◽  
M. Skålberg
Keyword(s):  
Ion Exchange ◽  
Cation Exchange ◽  
Cation Exchange Capacity ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Exchange Capacity ◽  
Alkaline Earth Metals ◽  
Crushed Granite ◽  
The Difference

AbstractThe possibility to use alkali metals and alkaline earth metals as slightly sorbing tracers in in-situ sorption experiments in high saline groundwaters has been investigated. The cation exchange characteristics of granite and some fracture minerals (chlorite and calcite) have been studied using the proposed cations as tracers. The results show low Kd’s for Na, Ca and Sr (∽0.1 ml/g), while the sorption is higher for the more electropositive cations (Rb, Cs and Ba). A higher contribution of irreversible sorption can also be observed for the latter group of cations. For calcite the sorption of all the tracers, except Ca, is lower compared to the corresponding sorption to granite and chlorite. Differences in selectivity coefficients and cation exchange capacity are obtained when using different size fractions of crushed granite. The difference is even more pronounced when comparing crushed granite to intact granite.

scholarly journals Crossover from metal to insulator in dense lithium-rich compound CLi4

2016 ◽  
Vol 113 (9) ◽  
pp. 2366-2369 ◽  
Author(s):  
Xilian Jin ◽  
Xiao-Jia Chen ◽  
Tian Cui ◽  
Ho-kwang Mao ◽  
Huadi Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Fermi Surface ◽  
Density Functional ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Density Functional Theory Calculations ◽  
Alkaline Earth Metals ◽  
Functional Theory ◽  
Surface Filling

At room environment, all materials can be classified as insulators or metals or in-between semiconductors, by judging whether they are capable of conducting the flow of electrons. One can expect an insulator to convert into a metal and to remain in this state upon further compression, i.e., pressure-induced metallization. Some exceptions were reported recently in elementary metals such as all of the alkali metals and heavy alkaline earth metals (Ca, Sr, and Ba). Here we show that a compound of CLi4 becomes progressively less conductive and eventually insulating upon compression based on ab initio density-functional theory calculations. An unusual path with pressure is found for the phase transition from metal to semimetal, to semiconductor, and eventually to insulator. The Fermi surface filling parameter is used to describe such an antimetallization process.

scholarly journals Cation-Exchange Equilibria in a Carboxylic Cation Exchanger and in Attapulgite Clay

1969 ◽  
Vol 44 (4) ◽  
pp. 221-235
Author(s):  
Gilberto García Monge
Keyword(s):  
Alkali Metals ◽  
Alkaline Earth ◽  
Cation Exchanger ◽  
Alkaline Earth Metals ◽  
Strong Electrolyte ◽  
Weak Electrolyte ◽  
Resin Phase ◽  
Carboxylic Groups ◽  
Marked Selectivity ◽  
Attapulgite Clay

Selectivity numbers for a synthetic cation exchanger of the carboxylic type (IRC-50) and the natural cation exchanger, attapulgite clay mineral, were determined for different pairs of cations. The results in IRC-50 for Na+-K+, Na+-Rb+, and Na+-Cs+ systems showed no marked selectivity. The resin phase was considered to act as a concentrated salt solution. Hence, differences in the selectivity numbers (K) were attributed to the differences in the activity coefficients in the concentrated resin-phase solution. In the alkaline-earth systems (Mg++-Ca++, Mg++-Sr++, and Mg++-Ba++) the resin showed more selectivity between its members than between those of the alkali series. The selectivity numbers were functions of the percentage of Mg in the resin. In the Mg++-Ca++ system, Mg++ appeared more strongly held at low percentages of Mg, whereas in the Mg++-Ba++ system, Ba++ appeared more strongly held at all percentages of Mg in the resin. These results were explained on the basis of formation of slightly dissociated complexes of the alkaline-earth metals with the carboxylic groups of the exchanger. The results in attapulgite clay for the Na+-K+, Na+-Rb+, and Na+-Cs+ systems showed marked selectivity. The selectivity numbers were functions of the percentage of Na in the clay. The differences in selectivity were greater in the Na+-Cs+ system than in the Na+-Rb+ system and, in the Na+-Rb+ system, greater than in the Na+-K+ system. The results were broadly understood on the basis of the bifunctional character of the clay. The differences in the selectivity numbers for the alkaline-earth metals in the clay (Mg, Ca, Sr, and Ba) are small as compared with those of the alkali metals. In general, the resin behaved as a moderately strong electrolyte with respect to the alkali metals. It behaved like a weak electrolyte with respect to the alkaline-earth metals. Attapulgite clay behaved like a weak electrolyte with respect to both the alkali metals and alkaline-earth metals. The results of the selectivitynumber curves for the clay resembled those of a bifunctional cation exchanger and a high cross-linkage resin.

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