Title screen

[References: 27 tit.]

A variant of the hygroscopic gravimetric technique is developed for the estimation of the total content of soluble impurities in solid crystalline chemical reagents, by considering water vapor sorption from an atmosphere with a definite relative humidity. The technique makes it possible to estimate the main component content of a substance, provided this substance is soluble in water. The proposed method is based on a simplified isopiestic measurement technique. An analyzed sample is divided into two portions: one is dried and weighed while the other is moistened up to 10–50% of the amount needed for the substance’s solubility. Both portions are then placed in cups in a desiccator and held for 24 h; water absorption of the initially dry sample is then determined. The feasibility of the method is demonstrated for NaCl and KCl systems (reagents and technical products) of different purities. The effect of impurities (KCl, MgCl2, LiCl) on water vapor absorption by NaCl is analyzed for the impurity contents ranging from 0.001 to 1 wt%. The method is recommended for the evaluation of quality of the initial reagents that are used in isopiestic investigations.