Physical-chemical Testing studies

The transition from solid to liquid phase takes place over temperature range. Therefore, the term "melting range" is often used and, in practice, the temperatures of the initial and final stages of melting are determined.

The sample is slowly heated in a boiling test tube placed within a liquid bath. The tube is positioned in close contact with a thermometer and contains a boiling capillary fused approximately 1 cm above its lower end. As the boiling point nears, bubbles begin emerging rapidly from the capillary’s lower open end. The boiling temperature is recorded as the point where, upon brief cooling, the bubble formation ceases and the liquid swiftly rises inside the capillary.

This guideline covers the determination of water solubility for essentially pure substances that are stable in water and non-volatile. The presence of impurities can significantly influence a substance’s solubility. Before testing, it is helpful to gather preliminary details such as the structural formula, vapour pressure, dissociation constant, and hydrolysis behaviour across different pH levels. Solubility can be measured using either the column elution method or the flask method.

The density is calculated from the difference in weight between the full and empty pycnometer and its volume. In the case of liquids, the dynamic viscosity should not be above 500 Pa.s.

The purpose of the study is to evaluate the surface tension of an aqueous solution by means of a Du-Nuoy Ring at 20 °C. The methods are based on the measurement of the force which it is necessary to exert vertically on a ring, in contact with the surface of the liquid, in order to separate it from the surface, in order to draw up the film that has formed.

This test guideline describes the procedure for the electrometric determination of pH of an undiluted aqueous solution or dispersion. The pH is determined by preparing 1% (w/v) solution or dispersion in distilled or de-ionised water at temperature same as of refrence substance used for calibration of pH meter.

The flash point is the lowest temperature at which a liquid releases enough vapor in a test vessel to form an ignitable mixture with air near its surface. A lower flash point means the liquid is easier to ignite. These test methods are useful for detecting contamination of relatively nonvolatile or nonflammable materials (above 49 Deg C) and flammable substances (upto 49 Deg C). They are conducted under controlled laboratory conditions to measure and describe the response of materials, products, or assemblies to heat and an ignition source.