The melting points of the anhydrides alternate in the opposite sense to those of the acids. Up to valeric the swing is wide but from there on it is small, each odd anhydride melting only about 2°above the mean evens. From heptylic to stearic, the average of the melting points of the anhydrides is 1.2°above the average of the acids. Above valeric the alternation is much smaller for the anhydrides than for the acids.The anhydrides crystallize in leafy plates and are soluble in the usual organic solvents. Limited quantities of the acids, usually one gram or less, prevented the determination of other properties.
Displacements, estimated intensities and depolarization factors have been measured for acetone, 2,6-dimethyl-4-heptanone, 5-nonanone, 7-tridecanone, 8-pentadecanone and 5tetradecanone. The results for acetone are compared with the previous data: Eight lines previously reported by one or more investigators are believed to be non-existent. A new weak line was observed at 1676 em-I. The depolarization factors obtained agree well with those reported by Simons, except that the 1356 line was found to be considerably less polarized and data for five additional lines were obtained.
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