No abstract

THE first successful production of carcinomata (in the skin of mice) using cigarette tar produced by a method designed to simulate the human habit, was achieved by Wynder, Graham and Croninger (1953). These results were confirmed subsequently by the same workers and by Sugiura (1956) using the same tar which was in all cases obtained from American cigarettes. More recently, Passey, Boyland, Pratt and Hieger (1956), applying a tar prepared from American cigarettes to mice under conditions comparable to those employed by the American workers obtained a much lower incidence of tumours than the latter after the first year of painting. The London workers had two mice presenting papillomata compared with fifteen mice bearing papillomata and two epitheliomata in the American workers' experiment (Wynder, Graham andCroninger, 1953, 1955) (Chalmers, 1954), (2) intra-pulmonary injection (Beck, 1954) and (3) injection into growing embryonic implants (Lyons, Peacock and Peacock, 1956). However, recently Blacklock (1957) produced an oat-celled carcinoma in the lung of one rat of eight given intrapulmonary inoculations of a tar from proprietary filters through which human subjects had smoked.Therefore it seems, from the latter experiment, that British cigarette tar may be carcinogenic, and (from the comparative series of experiments using British and American cigarette tars) that differences in carcinogenic potency exist between these tars.Wynder and Wright (1956 and 1957) showed that in the American cigarette tars the carcinogenic factors for mice and rabbits resided mainly, though not exclusively, in the neutral fraction, and further that the 3,4-benzpyrene content was insufficient to account for the biological activity of that fraction.The present paper records investigations into the composition of the fractions of "neutral tar" from British cigarettes which immediately precede and succeed 3,4-benzpyrene on the chromatographic column, there being evidence from chemical and biological investigations of other tars and oils (see discussion) for the occurrence of carcinogenic agents in these fractions.

Copolymerization of methacrylonitrile and «-methylstyrene was studied at 60°with free-radical initiation.Copolymer composition was determined by monitoring rate of loss of monomers from toluene solution, using gas-liquid chromatography. The reactivity ratios are ri(methacrylonitrile) 0.38, r2(«-methylstyrene) 0.54. A simple copolymerization model fits the data, although the ceiling temperature of poly(a-methylstyrene) is 61°. Mean sequences of this monomer in the copolymer are short and have an effectively higher polymerization enthalpy and ceiling temperature than high molecular weight homopolymer. A comparison of these results and previous data for copolymerization of styrene and «-methylstyrene with other reports based on chemical analyses of high molecular weight copolymer suggests that «-methylstyrene may be accumulating in low polymer.

SynopsisA semiempirical model for estimation of viscosities of concentrated polymer solutions' can be applied to mixtures of polymers in a common solvent. The data required for estimation of mixture viscosity are: solvent viscosity, polymer molecular weight, density, concentration, and intrinsic viscosity in the particular solvent. Calculated and experimental viscosities agree to within a few per cent for the relatively nonpolar systems for which comparative data are available. The model does not appear to be adequate for mixtures in which there are extensive hydrogen-bonding interactions.Results of the new model are equivalent to those of an empirical equation2 reported to be effective for fairly concentrated binary polymer mixtures.Specific interactions between polymeric solutes can be conveniently assessed by comparing measured mixture viscosity to that calculated from the model presented. It is not clear, however, that such assessments have any fundamental significance, since the interactions which are calculated depend on the assumptions inherent in the estimation of the "ideal'' mixture viscosity. The same reservations apply to other models which have been proposed for this purpose.

The free radical copolymerization of methacrylonitrile, styrene, and a-methylstyrene was studied at 60 OC in toluene solution. Copolymer composition was calculated from the composition of the unreacted monomers, as measured by g.1.c. Reactivity ratios measured previously for the three monomer pairs involved were used with the simple terpolymerization equation to predict polymer composition. Agreement between predicted and experimental polymer compositions was satisfactory. The behavior of a-methylstyrene can be described by a simple model without reference to ceiling temperature or penultimate effects because sequence lengths of this monomer in the terpolymers are short.A true azeotropic feed composition was not investigated, but several monomer mixtures produced copolymers with compositions which varied so little from that of the feed that the systems could be considered to be azeotropic for practical synthetic purposes. This behavior is in accord with expectations.Analytical accuracy of the gas chromatographic techniques was examined and means are suggested to make the best use of this method in copolymerization studies.La copolymCrisation par radicaux libres de methacrylonitrile, styrene, et a-methylstyrene a ete etudiee a 60 "C en solution dans le toluene. La composition du copolymere a ett calculee a partir de celle des monomeres restants par c.g.1. Les rapports de reactivite precedemment mesurts pour les trois monomeres impliques pris deux a deux, ont CtC utilises dans la simple equation de terpolymtrisation pour prtvoir la composition du polymtre. Un accord satisfaisant entre les compositions calculee et trouvte a etC obtenu. Le comportement de I'a-mCthylstyrene peut itre decrit par un modele simple sans faire reference a la temperature "de plafond" ou a des effets prtterminaux car !es longueurs des sequences de ce monomtre dans les terpolymeres sont courtes. La composition d'une alimentation azeotropique vraie n'a pas Ctt recherchee car de nombreux melanges de monomeres ont donne des copolymtres dont la composition differe tellement peu de celle de I'alimentation, qu'il est possible de considtrer ces systtmes comme Ctant azeotropiques, a des fins de synthese pratique. Cette attitude est conforme aux previsions.La precision analytique des techniques de chromatographie en phase gazeuse a ete examinee et des moyens ont ett proposes afin de faire le meilleur usage de cette methode a des etudes de copolymtrisation.