Abstract
The sharpness and reproducibility of the gallium melting point were studied, and the melting temperature of gallium in terms of IPTS-68 was determined. Small melting-point cells designed for use with thermistors are described. Nine gallium cells including three levels of purity were used in 68 separate determinations of the melting point. The melting point of 99.99999% pure gallium in terms of IPTS-68 is found to be 29.7714 ± 0.0014 °C; the melting range is less than 0.0005 °C and is reproducible to ±0.0004 °C.
Abstract
The process of formation and melting of neoprene crystallites was investigated by the polarized light scattering method. Conclusions about the nonreversibility of the crystallization and melting processes were drawn on the basis of angular distribution measurements of depolarized and polarized components of light scattered from polymer films. The appearance of a relatively small number of large crystallites is characteristic for the initiation of crystallization; further development of crystallization is accompanied by a decrease in the size of the crystallites. All crystallites disappear simultaneously during the melting process. The size of the crystallites determined by microphotography corresponds approximately to the particle size determined by the formula for isotropic, spherical particles. A method for the determination of the melting range of crystalline polymers is proposed.
Laboratories measuring melting temperature according to USP<741> Melting Range or Temperature, must comply with the amended calibration and adjustment requirements described in this regulation. Compliance is ensured by adjusting the instrument with secondary reference standards, traceable to USP, followed by verification of accuracy using USP primary reference standards.
Determination of melting temperature of slagmaking mixtures for billet CCM mold by differential thermal analysis method