The empirical parameters of the polarity of solvents which have been determined recently are reviewed: Y‐values (Winstein, Grunwald), X‐values (Gielen, Nasielski), Ω‐values (Berson, Hamlet, Mueller), Z‐values (Kosower), ET‐values (Dimroth, Reichardt, Siepmann, Bohlmann), R‐ and S‐values (Brownstein). Their field of application and interrelationships are discussed. The theoretical principles of the solvent effect on the reaction rate and light absorption of organic compounds are briefly described, and mention is made of attempts to correlate the physical characteristics of the solvent with the empirical parameters.
Es wird eine Ubersicht iiber die in den leizfenJahren ermit telten empirischen Parameter der Losungsmittelpolaritat gegeben: Y-Werte ( Winstein, Grunwald), X-Werte (Gielen, Nasielski), 0-Werte (Berson, Hamlet, Mueller), Z-Werte (Kosower), ET-Werte (Dimroth, Reichardt, Siepmann, Bohlmann), R-und S-Werte (Brownstein). Ihr Anwendungsbereich und ihre Korrelationen untereinander werden diskutiert. -Die theoretischen Grundlagen des Losungsmitteleinflusses auf Reaktionsgeschwindigkeit und Lichtabsorption organischer Verbindungen werden kurz erlautert und Versuche erwahnt, physikalische Kennzahlen der Losungsmittel rnit den empirischen Parametern in Beziehung zu bringen.
A two-dimensional load-extension tester for woven fabrics has been constructed. The ap paratus imposes simultaneous extensions on a sample in two mutually perpendicular directions. A strain-sensing element measures the internal strain developed in the homogeneously strained region as a function of the dynamically varying load. Preliminary results indicate important dif ferences in behavior of fabrics under one-dimensional tests and under two-dimensional tests. The latter are believed to simulate better the conditions that a fabric sustains in actual use.
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