Methorics of the Precipitation Processes. XIX. Fluorescence of Sodium Fluoresceinate, Rhodamine B and their Mixtures, as a Function of Hydrogen Ion Concentration in Water Solutions

The fluorescence of sodium fluores ceinate and rhodamine B has been measured over a wide range of pH. The results obtained are in full agreement with the absorption measurements reported by previous a uthorss.13. Precipitation maximum at about pH 3 is identical with the minimum of fluorescence intensity for the predominant form of fluorescein i.e. the neutral molecule. The precipitation limit at about pH 5 is characterized by the equilibPium between the neutral molecule and the monoanion ; the di s continued curve at pH 7 represents the equilibrium between the monoanion and the dianion. Fluorimetric curves of divalent cation of rhodamine B r emain practically constant over a wide rang e of pH. In the system consisting of sodium fluoresceinate and rhodamine B it has been shown that the phenomenon of isoelectric precipitation takes place by »e quivalent body« formation . The concentrational relationship between the interacting ions is strongly influenced by the hydrogen ion concentration

The Theory of Crystallization as Viewed from Experiences with Electrolytic Systems

By reviewing older results, especially those of v. Weimarn and Oden, on the examples of differences between sparingly soluble sulfates and halides, new approaches to the diagramatical presentation of the characteristic features of precipitation and crystalization processes and structures were used. Namely, in order to enable comparison, various systems were observed under fixed temperature and pressure in developmental stages according to their position in the so-called "cube of dilution", and were represented as specific time-dependenf "precipitation bodies". It is pointed out that the emergence of the solid phase from solution is a complex phenomenon where a large number of nonequilibrium states may interfere with each other in such a way that already the concentrational parameters of various species in preembryonation stages, as well as in the methorical layer of embryos, nuclei, primary particles, and secondary aggregates in formation, reflect both the direct growth of smaller units, and their aggregation controlled mainly by stability/instability relationships. In order to explain the critical steps (the role of "new parts" and "surfaces of discontinuity" of Gibbs) in the transformation of the homogeneous solution to the heterogeneous system, schemes of various parts of chemical potential in ionic interactions, the "surfaces of discontinuity" in the methorical layer, the boundary of the growing crystal, and the stability/instability conditions of the ,emerging embryos, nuclei, or primary particles in solution, are given

Methorics of the Precipitation Processes. XX. Silver Salts of Dyes of the Fluorescein Group (Fluorescein, Eosin, and Erythrosin) in Aqueous Medium

The precipitation systems consisting of aqueous solutions of silver nitrate and the dyes of the fluorescein group (fluorescein, eosin, and erythrosin) have been investigated by means of tyndallometric measurements by systematically varying the concentration of the precipitating components. The general and three- dimensional precipitation diagrams of the »precipitation bodies« show very characteristic features. The silver fluoresceinate shows two regions; the precipitation region and the region of clear systems are divided by a straight line with the slope indicating the formation of Ag2-fluoresceinate in accordance with the ionic solubility law. The silver eosinate systems show two precipitation regions divided by a narrow region of clear systems. With respect to both the limits of the clear equivalency region and the two precipitation regions, the silver erythrosinate systems are even more specific. An attempt has been made to give an explanation for the negative charges of primary particles in spite of the large excess of silver ion, as well as for the characteristic shape of the »precipitation bodies«

The Behaviour of the System: Gelatin-Ferric Chloride-Neutral Electrolyte-Hydrochloric Acid or Sodium Hydroxide in an Aqueous Medium. III. The Behaviour of the Simpler System: Ferric Chloride-Sodium Chloride-Sodium Hydroxide in an Aqueous Medium

The system FeC13-NaCl-NaOH is one of the simpler systems composing the four component system gelatin - FeC1 3-NaC l-HCl or NaOH. It is formed by addition of the NaCl component to the system FeC1 3-NaOH. The precipitation curve of the system FeC1 3- -NaCl-Na OH consists of only one maximum. The coagulating action of 6 · 10-1 N NaCl causes the joining of two separate maxima occurring in the system with no NaCl added. The summary diag r ams represent the regions of the precipit ation curve in dependence -on the concentrations of the FeC 13 and NaOH components and the corresponding pH values. At certa in concentrations of the FeC 13 component, the precipitation maximum is extended far into the positive (acid) s ide

Solid/Liquid Interfaces

An introductory paper to the material of a scientific conference has many purposes. In few words it should give an orientation about the circumstances, origin and goals of such an organized attempt to concentrate attention on one specially chosen scientific topic; further, it is expected that something of the general historical background should be mentioned; moreover, it is meant to give a frame for the presentation and discussion of relevant and pertinent material and for drawing conclusions

Methorics of Precipitation from Electrolytic Solutions as Revealed through Relationship between Concentrational Factors and Kinetics of Solid Phase Formation

For an explanation of the pecularities of precipitating systems they are treated as composed of five subsystems: (i) formation of complex species (simple and monomers, as well as polynuclears and polymers); (ii) embryonation (aggregates without core formation); (iii) nucleation and direct growth (the growing core); (iv) micellation (formation of primary particles with colloid individuality); and (v) secondary structures of micro and macro particles. It is assumed that the transition from ideal liquidus structures (ILS) to ideal solidus structures (ISS) usually proceeds through stages characterized by the development of methorical structures and textures (MS & T). Applying the method of continuous variation of concentration of precipitating components the characteristic four types of precipitation bodies (PB, as a plot of logarithm of concentration of the cationic component against anionic one) are used for description and discussion of experimental results. For illustration some contours of PBs are given (silver bromide; silver salts of fluoresceine group; uranyl phosphates; iron-III hydroxides, thorium hydroxides, hydroxides of lanthanides, all in aqueous solutions). In discussing the morphology of the precipitates obtained by »solution aging« or under the conditions of »homogeneous« precipitation, it was pointed out that the phenomena may be explained by taking into account the role of subsystems and the discontinuities caused by aggregation of submicrons into larger units

An Analysis of the Present State of Chemical Literature and the Need for the Establishment of an International Chemical Periodical

The production, dissemination and assimilation of new knowledge are the conditiones sine qua non for the existence of science. The fact, that modern science was born almost simultaneously with the invention of printing emphasizes the above statement. Thus the first great success of the union of craft and theoretical knowledge removed the old drawbacks of isolationism. That was the origin of all other similar fruitful unions

Methorics of the coagulation processes. I. Mechanism of coagulation of hydrophobic sols

In order to emphasize the necessity that theory should embrace the whole experimental evidence about coagulation, a short review of the findings and empirical rules concerning the coagulation phenomena are given. Among them has been pointed out Schulze - Hardy\u27s rule, the relationship between the ionic size and the coagulation value, Burton - Bishop\u27s rule, the evidence about the adsorption of the stabilizing ions, the observations of electrophoretic mobiIity of the coagulating particles, the effects of ionic antagonism, the relationship between the coagulation value and the coefficient of the activity of the electrolyte, and others