Über das dielektrische Verhalten von Oxydhydraten

Abstract

2) E. Rrmer et R. Sgnartamattr, loc. cit. 3) Des indications plus detaillBes seront donnhes dam la thkse de E. I J O W~, Recherches sur l'absorption des gaz nitreux par le gel d'alumine, la chaux et la glucine.

The Constitution of Colloidal Systems of the Hydrous Oxides.

“…In support of his criticism of Willstatter's point of view Posnjak showed that samples of the so-called orthoand meta-stannic acids give identical x-ray diffraction patterns, which in turn are identical with that of the mineral cassiterite, anhydrous Sn02. This result has been confirmed by Yamada (70), Forster (13,16), Hiittig and Dobling (18), and others, so that there is no question about the facts. The orthoand meta-acids (a-and /3-oxides) are not isomers but are structurally identical stannic oxide with more or less adsorbed water.…”

A Dielectric Study of the Gelatin–Water System: Anomalous Dispersion in Bound (Oriented) Water.

“…From this result it was concluded that the origin of these singular dielectric properties is a polarization of the region at or near the interphase, by the external field, in the direction parallel to the interphase. It has been known for a long time that the dielectric constant of many colloids is much higher than that of water (13,14,24,25,27,28,30,32,44)'. One of the best known systems is that of colloidal vanadium pentoxide, first investigated by Errera (13,14).…”

Böhmite and Bayerite

“…This bayerite (A1203 • 3H20), to the properties of which we shall refer later, also belongs to the -series of Haber, since it produces cubic -oxide on complete extraction of water. It is metastable at room temperature in contrast to gibbsite (hydrargillite) (9,10,11,17), but stable in comparison with bohmite (3,20,24). It is probably identical with the substance designated as ß-1203•3 20 by Edwards and Tosterud.…”

“…As has since been definitely ascertained by various observers, bohmite is the first product of aging aluminum hydroxide gel precipitated from solutions of aluminum salts with alkali. This is shown with great clearness by the work of Fricke and Meyring (14), who investigated the aging of aluminum hydroxide in alkaline media by determinations of solubility, pH measurements, and x-ray photographs, as also by the experiments, combined with x-ray photographs etc., conducted by Havestadt and Fricke (20) in regard to the dielectric constants of hydrous hydroxide suspensions depending on the state of aging. Kohlschütter and his collaborators (24) also found in the course of their extensive investigations into the aging of fresh gels that the formation of a crystallized trihydrate can never overtake the formation of the "ß-gel" (a term used (24, 32) for a very slightly reactive gel which sometimes shows the x-ray lines of bohmite).…”

“…The angles fora pure bayerite for copper radiation are given by Fricke (10). Bayerite is produced from bohmite gel ("/3-gel" and fresh bohmite) by aging, production being slow under cold water (3,20,24), but rapid under dilute alkali (10,14). In an intermediate stage of the aging, according to Kohlschütter and collaborators (24), "somatoids" form from minute needles of bayerite, which are either wholly or partly surrounded by /3-gel (bohmite gel).…”