The possibilities of using cupriethylenediamine (or cuprammonium hydroxide) solution as solvent in molecular fractionation of cellulose was investigated. From the results the following conclusions could be drawn. (1) A real fractionation based on different dissolving power of cuene or cuoxam solutions of different copper concentration seems not to be possible. The results of such fractionations presented in the literature seem rather to be due to a fractionation on the basis of the accessibility. A clear relationship seems to exist between molar concentration of the excess copper in solution and, respectively, per cent dissolved substance and [η] value of the undissolved substance. (2) Precipitation of cellulose from a cuene solution by means of an acid does not bring about a fractionation according to chain length. (3) Fractionation takes place according to chain length when the precipitation of cellulose from a cuene solution is carried out by means of organic liquids, among which propanol has proved to be the most suitable one. In this case the precipitation is caused by decrease of the degree of solvation of the cellulose‐cuene complex. (4) Fractionation can be brought about by raising the temperature of a propanolcontaining cuene solution of cellulose. (5) Considering the depolymerization of cellulose in cuene and cuoxam solutions these solvents cannot be regarded as suitable for determination of the chain length distribution of cellulose.
A method has been developed to determine the distribution of the molecular weights of the high polymers.' The basis of this method is the separation of the fractions by lowering the temperature of a solution of the polymer containing a precipitant. Experiments have shown that the reproducibility of the method is good. By using a constant solvent/ precipitant ratio in different fractionations, it is possible, from the temperature of precipitation, to estimate approximately the limiting viscosity number of the fraction obtained. Z U SAMMENFAS S UN G:Es ist eine Methode zur Bestimmung der Verteilung der Molekulargewichte von hochpolymeren Stoffen entwickelt worden. Den Grund fur diese Methode bildet die Trennung der Fraktionen durch Erniedrigung der Temperatur einer Losung des Polymeren, die ein Fallungsmittel enthalt. Wie ausgefiihrte Versuche-gezeigt haben, ist die Reproduzierbarkeit der Methode gut. Durch Verwendung eines konstanten Verhaltnispes Losungsmittel/Fallungsmittel in verschiedenen Fraktionierungen, ist es moglich, die Grenzviskositatszahl der erhaltenen Fraktion aus der Fallungstemperatur annahernd zu schatzen.
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