Analysis of zone-melted ultra-pure organic compounds: a new quantitative differential thermal analysis method.

A method for the rapid quantitative determination of impurities in ultra-pure organic compounds is described. It is based on the difference in slopes of the curves obtained when the difference in temperature between the sample and a reference shield is plotted against time. The results are compared with those obtained by thermal analysis.

Theoretical considerations in the zone melting of organic substances Analysis of the diffusion gradient.

Further evidence is gathered in the theory of the zone melting of organic compounds under ideal equilibrium conditions by a kinetic study of the diffusion gradient in the melt zone. A mathematical analysis is developed for the concentration distribution of impurities in the moving molten zone, which yields an expression for the concentration gradient at the liquid-solid recrystallisation interface. These expressions describe the transport process and a measure of the rate of segregation of impurity at the recrystallisation interface.