The polymerization of methyl methacrylate initiated with ALBN and inhibited with cupric chloride in DMF has been studied at 60°C. Cupric chloride proved to be an " ideal " inhibitor, the post-inhibition rate being equal to the rate obtained in the absence of inhibitor. From a simple inhibition period against cupric chloride concentration plot, the rate constant for the decomposition of AIBN into free radicals was 1.38 x 10-5 sec-1. From a study of the period of acceleration following complete inhibition, a value of 1050 was found for the ratio kx/kp, where kx is the rate constant for the reaction between polymethyi methacrylate radicals and cupric chloride. This leads to a value of 7.7 x 105 1. mole-1 sec-1 for kx at 60°, which is much higher than that for the corresponding reaction with ferric chloride, and is of the order of magnitude of rate constants for radical-radical interaction.

The polymerization of methyl methacrylate initiated with AIBN and inhibited with cupric bromide in DMF has been studied at from 40-70°C. Rate constants for the initiation reaction, obtained by the inhibition period method, were 6.2 x lo-', 3.7 x 1.42 x and 8 x s-l at 40, 50, 60 and 70°C respectively, yielding an activation energy of 137.5 kJ mo1-l. The acceleration period

A study has been made of the chemical composition of chill-hazes and oxidationhazes of certain commercial and experimental beers. In addition to amino acid and sugar units, the hazes have been shown unequivocally to contain tannin derived both from malt and from hops. The hazes have been shown to be heterogeneous both by means of chemical fractionation and by ultracentrifugation. Spectrographic exami nation of the ash from certain specimens revealed that the hazes contained concen trations of heavy metals, particularly copper, iron and aluminium, which were high relative to their concentrations in the beers giving rise to them. The study was extended to include some factors which affect the rate of formation of hazes in beers. Heating of hazy beers resulted in solution of the haze already present slowly followed by the precipitation of a further haze with solubility characteristics different from those of the original. The effect of cooling beers which had been heated for a brief period at 70°C. was also studied. It was found that the rate of formation of haze was lower after rapid cooling of the beer than after slow cooling. Finally, the rate of formation of haze was, within limits, independent of the amount which had already separated from solution, suggesting that there is a considerable reserve in the beer of potential haze constituents.General Composition of Hazes 36 mg. per litre of lager beer (average 13-4

The cross-linking of polyvinylchloride in ethyl benzoate solution has been studied over the temperature range 178 to 212°C. in an atmosphere of nitrogen. The effects of variation in polymer concentration and in molecular weight of the polymer on the time taken for the polymer solution to gel have been observed, and the rate of crosslinking has been calculated from such data by applying FLORY'S theory of gelation. Over the above-mentioned temperature range the expression for the rate of crossbond formation was found to be 2.0.103 e-23,000/RTci crossbonds/l:sec., where c w is the polymer concentration in monomoles /l. This expression applies to polymer samples with number average degrees of polymerization varying from 192 to 905, and may well apply to an even wider range.The addition of free radical initiators and free radical inhibitors had little effect on the time of gelation whereas oxygen retarded or prevented gel formation. The results in general support the view that the crosslinking process proceeds by a non-radical mechanism, and involves a random condensation reaction between two structural units in different polymer molecules with the elimination of HCI. ZUSAMMENFASSUNG:Die Vernetzung von Polyvinylchlorid wurde in Benzoesaureathylester-Losung unter Stickstoffatmosphire im Temperaturbereich 178 bis 212°C untersucht. Die in Abhangigkeit von der Konzentration und dem Molekulargewicht des Polymeren beobachtete Zeit, bis Gelierung auftrat, diente zur Berechnung der Vernetzungsgeschwindigkeit nach der FLoRYschen Gelierungstheorie. Danach ist innerhalb des angefuhrten Temperatubereiches die Geschwindigkeit der Vernetzungsbriickenbildung 2,0.103. e-23000/RT.ci Vernetzungsbriicken/l.sec, wobei c, die Polymerkonzentration in Monomolen/Z bedeutet. Dies gilt fur Polymere mit dem Zahlenmittel des Polymerisationsgrades 192 bis 905 und ist vermutlich auch auf3erhalb dieses Bereiches gultig.Zugesetzte freie radikalische Initiatoren und freie radikalische Inhibitoren hatten eine geringe Wirkung auf die Gelierungszeit, wahrend Sauerstoff die Gelbildung verzogerte oder verhinderte. Die Ergebriisse weisen im allgemeinen auf einen nicht radikalischen Mechanismus beim Vernetzungsvorgang hin und lassen sich durch eine zufallige, mit einer HCl-Abspaltung verbundenen Kondensation zwischen zwei Struktureinheiten verschiedener Polymermolekeln erklaren.

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