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The specific heat and the specific volume of the different crystal modifications of poly‐1‐butene were investigated. Modification III, the crystalline structure of which is still unknown, was obtained by precipitating the benzene solution with methyl acetate. At 101°C. it is transformed into the tetragonal phase which melts at 121.5°C. The specific heat of the rhombohedrie structure, which was obtained from the melt by cooling and storage over a long period, increased evenly with a rise in temperature Up to its melting point; by immediately measuring a freshly cooled melt, the specific heat of the tetragonal modification (at least above 80°C.) was obtained. A predominantly atactic material which had been stored for a long period, indicated the melting at 87°C. of the small fraction of the rhombohedric crystals. The investigations were supplemented by dilatometric measurements. By means of the degree of crystallinity thus obtained, the heats of fusion were calculated and compared with values from measurements conducted on the melting point depression of mixtures.

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