OSMOTIC AND ACTIVITY COEFFICIENTS OF SOME AQUEOUS RARE-EARTH CHLORIDE SOLUTIONS AT 25°C I

摘要

The least square equations obtained for the osmotic coefficient as a function of molality for erbium and yttrium chloride solutions resulted in a mean deviation of 0. 0019 and 0. 0024 in the osmotic coef-ficient, respectively, for the two solutions. These deviations at a median osmotic coefficient are 0. 08% for erbium chloride and 0. 10% for yttrium chloride. Of course, the percent error in the osmotic coef¬ficient is larger for the most dilute solutions and lower for the saturated solutions. The corresponding error in the activity coefficient was deter¬mined to be about 0. 0010 in the logy±, while the activity coefficients were in error by 0. 008 for y^ = 0. 3261 in the dilute solution range or by 0. 020 for y± = 9. 760 in the most concentrated solutions of erbium chloride. All deviations in the activity coefficient gave an almost uni¬form mean deviation of 0. 23%. These deviations in the activity coeffi¬cient correspond with those expected from the experimental procedure of this type of research. The errors concurred are:the error in analysis of each solution was of the order of 0. 05% for molalities greater than.one and from 0.10 to 0.15% for molalities less than one;and the reliability of the reference osmotic coefficient data is about 0. 0010 in the osmotic coefficient. Since the molalities of two solutions must be known for the calculation of the rare-earth osmotic coefficient, a mean deviation of 0. 0020 in its osmotic coefficient determined in this research is within the experimental precision of the isopiestic method.