Some physical constants of normal saturated fatty acids and their methyl esters

The series of the normal saturated fatty acids and their methyl esters with 5 to 20 carbon chain atoms was synthesized and careful purified, mainly by fractional distillation of the methyl esters in columns with up to 58 theoretical plates. The purity was checked with the aid of melting curves determined in a microcalorimeter and proved to be 96.6% or better. Refractive indices were determined and can be represented by with an accuracy of 5 units in the fifth decimal place (c = number of carbon chain atoms). Densities, accurate to 1 unit in the fourth decimal place, can be represented by Boiling points can be given by b.pt. 20 mm for the methyl esters (c> 5), accurate to 0.1 °. From our data, combined with literature values, the molecular refractivity of the CH2 group in an aliphatic chain calculated according to Lorentz-Lorenz. was determined at 4.64 at room temperature. In addition, melting and transition points, and heats of fusion and transition were determined.