Capillary melting point apparatus with heat-free hysteresis effect of uniform temperature field

Abstract

The invention relates to a capillary melting point apparatus with heat-free hysteresis effect of a uniform temperature field, adopting a liquid heating medium for electric heating and comprising a heating system and a temperature measuring system. The heating system takes a quartz vacuum heat-insulated cup as a vessel, is provided with an upper electric heating wire and a lower electric heating wire and is heated by an intermediate medium of silicone oil; a detachable temperature-sensing element of the temperature measuring system is fixed between the upper electric heating wire and the lower electric heating wire, the tail end of the temperature-sensing element and a connecting lead are encapsulated in a stainless steel sleeve tube, and the main part of a Pt100 industrial platinum resistance thermometer of the temperature-sensing element is exposed out of the sleeve tube to directly contact with the medium; a platinum resistor is connected to a digital voltmeter through a lead at a four-wire system; and during measurement, the resistance of completely melt samples is recorded and a temperature value is obtained by the corresponding relationship of the resistance and the temperature. The temperature-sensing element can directly correct the temperature, is free from using melting point reference materials for correction and has convenient correction. The thermal hysteresis effect is corrected through theoretical calculation, thus the thermal hysteresis system error is eliminated in the full melting point measurement.

Description

technical field [0001] The invention relates to a melting point instrument, in particular to a capillary melting point instrument with a uniform temperature field and no thermal hysteresis effect of a thermometer. Background technique [0002] The melting point of a substance is the temperature at which the substance changes from solid to liquid. The complete melting point of a substance refers to the temperature at which a substance completely transforms from a solid state to a liquid state at a certain heating rate. The role of melting point is: First, qualitative identification of organic compounds. Since different organic compounds have different melting points, the melting point can be used as a convenient method to identify organic compounds. Second, determine the purity of organic matter. The melting point of organic matter containing certain impurities is lower than that of pure organic matter, and the difference in melting point is proportional to the content of ...

AI Technical Summary

Problems solved by technology

For a melting point apparatus using a liquid heating medium, the heating element is usually at the bottom of the container, and the non-uniform temperature field in the vertical direction (about 0.40°C / cm) is caused during the heating process, resulting in a systematic error of 0.20°C in the melting point determination

[0005] Therefore, it is urgent to develop a capillary melting point instrument with a uniform temperature field and no thermal hysteresis effect of the thermometer to solve the problem of large errors in the current melting point determination system.

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