Ernst A. Hauser

Urinary colloids in the prevention of kidney-stone formation.

THE nature and process of kidney-stone formation has puzzled the medical profession for a long time. In the sixteenth century Paracelsus expressed the opinion that a material obtained from food con...

Colloid Science of Montmorillonites and Bentonites

In 1847 the name “montmorillonite” was given to a rose-red, clay-like mineral forming nests in a brown clay at Montmorillon, France. The first analysis, reported by Salvetat, gave 49.4 percent to SiO2, 19.7 percent to Al2O3, 0.8 percent to Fe2O3, 0.27 percent to MgO, 1.5 percent to CaO, 1.5 percent to alkalies, and 25.67 percent to H2O. Much later a substance which was originally called “taylorite” after William Taylor, who was the first to draw attention to it, was finally designated as “bentonite” because it was first found in the Fort Benton series of rocks in Montana. The most characteristic mineral component of bentonite is crystalline and definitely montmorillonite.

Bildung und Struktur von Silikagel

ZusammenfassungZwei grundlegend verschiedene Reaktionen finden gleichzeitig statt, wenn man eine Lösung von Orthokieselsäure altern läßt. Die Polymerisation beruht auf der Befriedigung des Koordinationsbedarfes, und die Kondensation beruht auf Abspaltung von Wasser zwischen zwei eng benachbarten OH-Ionen. Abhängig von der individuellen Geschwindigkeit dieser beiden Reaktionen und ihrem Zusammenwirken erhält man Silikagele mit außerordentlich verschiedenen Eigenschaften.

THE COLLOIDAL NATURE OF ANTIBIOTICS

Just about thirty years ago, it was discovered that salts of higher fatty acids will react like simple electrolytes if present in great dilutions, but in higher concentrations will exhibit properties typical of the colloidal state of la It was at that time that the term “colloidal electrolyte” was introduced into scientific terminology. Colloidal electrolytes are salts in which one of the ions has been replaced by a highly charged, heavily hydrated ionic micelle, which exhibits equivalent conductivity that is not only comparable with that of a true ion but may even amount to several times that of the simple ions from which it has been derived. In other words, this ionic micelle is a typical, but very highly charged, colloidal particle of very great conductivity. Some of the very numerous substances which must be recognized as belonging to this group are the protein and gelatin salts, the higher sulphonic acids, in fact, most substances of high molecular weight or those containing long carbon chains which are capable of splitting off an ordinary Just as very little credence was given to these statements a t that time, a discovery reported quite recently, that most antibiotics must also be classified as colloidal electrolytes,s. has caused considerable controversy among scientist^.^ 1 In a paper on “Colloid Phenomena In Bacteriology,” written twentyseven years ago,I8 one finds the following: “However diverse the action of growth stimulants or however complicated the mechanism by which death is caused in the microorganisms, nevertheless, in many cases, a t least in the preliminary stages, the bacteria may be regarded as simple colloidal systems. The more recent developments in the study of colloidal systems have emphasized the important influence of the interfacial surface on colloidal reactions. With bacteria presenting the extended surface of colloidal systems, adsorption a t the interface is of primary importance. If any substance added to the medium lowers the interfacial surface tension, then the surface concentration, in accordance with Gibbs’s equation, will be greater than the bulk concentration. It is evident that if the added solute has a great effect on the surface tension, the surface concentration may become quite high. The inhibiting materials produced during bacterial growth may be soaps, fatty acids, and higher aliphatic alcohols. The adsorption of organic substances from solutions by bacteria is to be ascribed to the presence of certain groups in the molecules. The growth rate of microorganisms is greatly influenced by the concentration a t the bacterium’s surface of the various substances present. The surface concentrations may already be considerable, even when scarcely detectable amounts are present in the bulk of the medium.” Taking this citation into consideration and reviewing it critically in the light of what has been said about colloidal electrolytes, it seems obvious that it did not receive the attention it deserved. If it had, more emphasis

Penicillin — ein kolloider Elektrolyt

Zusammenfassung1.Es wird auf die Aehnlichkeit von Penicillin und Seifen vom kolloidchemischen Standpunkt aus hingewiesen, und es werden Gründe für seine Klassifizierung als kolloider Elektrolyt gegeben.2.Die Ergebnisse rein chemischer und physikalischer Forschung bezüglich der chemischen Formel für Penicillin werden kurz besprochen.3.Es wird auf Ergebnisse medizinischer Forschung, wie die antibiotische Aktivität von Penicillin erhöht werden kann, und wie es wirkt, hingewiesen.4.Die kolloidchemischen Eigenschaften von Penicillin-Solen, wie Oberflächenspannung, elektrische Ladung, Ionenaustausch und Adsorption werden eingehend besprochen.5.Es wird, unter Hinweis auf die erhöhte Wirksamkeit von Streptomycin in Anwesenheit kapillaraktiver Chemikalien, auf die Bedeutung der Kolloidchemie für das Gebiet der Antibiotica hingewiesen.

Creaming of rubber latex

Abstract The creaming of rubber latex was first observed as far back as 1824 when Hancock, working with what was probably Castilloa latex, observed that if this latex is well shaken with three or four times its volume of water and then allowed to stand, a separation into two layers will take place which thus effects a purification of the dispersion. This phenomenon, reported again by Faraday in 1825, is a spontaneous creaming which takes place with latices of large particle size. Latex of Hevea brasiliensis will not cream spontaneously in this manner and, although other methods of inducing creaming, such as the addition of caustic alkali, were previously known, it remained for Traube in 1924 to patent the first method which would prove satisfactory for commercial concentration. Rahn had reported in 1922 that the natural creaming of milk could be greatly accelerated and made more complete if small amounts of gelatin or of similar hydrophilic colloids, such as gum tragacanth, gum arabic, peptone or albumen,...

Molecular Fractionation by Diffusion of Guayule and Cryptostegia Rubber

Abstract In general it can be said that the molecular-size distribution of Cryptostegia as well as guayule rubber is very much different from that of Hevea. The length of the Cryptostegia chains are within the range of the Hevea chains, but their distribution is not as even as those of the latter. Guayule must be considered as a rubber of much lower molecular weight.

A Contribution to the Theory of Thixotropy

Although a careful review of literature has revealed that the phenomenon now termed “thixotropy” had already been observed some years ago by various research workers, the first systematic study of this phenomenon is of comparatively recent date as well as the denomination, which is taken from the Greek works, “ϑιξομαι” = “by touching” and “τζ′eωπω” = “to change,” and which gives a rather accurate conception as to what this phenomenon refers. For example, it has been found that certain colloids present in the form of a plastic gel can be spontaneously and adiabatically liquefied by simple mechanical influence, e. g., shaking, and that such liquefied gels, now being in the sol condition, will, if left quiet, return to the original plastic solid gel. This sol‐gel‐transformation can be repeated consecutively many times without changes in setting time, if all conditions are kept constant during the experiments.

The Morphology of Rubber Latex Particles. A Critical Review

Abstract The morphology of the hydrocarbon particles of latices obtained from several rubber producing plants has in recent years again been the subject of studies applying the most modern tools of research. Lucas used for his studies an ultraviolet light microscope and later ultramicrocinematography. Quite recently Hendricks, Wildman, and McMurdie applied electron microscopy for the first time for this purpose. Since some of the deductions in regard to the form and structure of latex particles which have been drawn from these studies differ in several respects from conclusions based on micrugic and ultramicroscopic studies, some of which were reported twenty years ago, it seems advisable to clarify the picture. Such clarification is most important at present, because a better knowledge of the morphology of natural and synthetic rubber latex particles might offer a valuable aid in explaining some of the differences in the properties of these hydrocarbon polymers, which are not readily explainable on the b...

Zur Kenntnis der allgemeinen Funktion zwischen Viskosität und Teilchengrö\e

ZusammenfassungEs werden Viskositätsmessungen an verdünnten Bentonitsolen von bekannter Teilchengrö\e (10–200 mΜ) mitgeteilt. Die Viskosität nimmt mit zunehmender Teilchengrö\e bis zu einem konstanten Wert ab. Es liegt hier also ein weiteres Beispiel für den noch wenig untersuchten absteigenden Ast der von Wo. Ostwald postulierten Maximumkurve der allgemeinen Funktion zwischen Viskosität und Teilchengrö\e vor. Der au\erordentliche Anstieg der Viskosität im Gebiete der Fraktionen mit kleinstem Teilchendurchmesser, sowie die, im Vergleich zum reinen Dispersionsmittel, noch verhältnismä\ig hohe Viskosität der groben Fraktionen wird auf den hohen Hydratationsgrad des dispersen Anteiles zurückgeführt.