Abstract
In this paper, a study was conducted to examine the crystallizing temperature of NaOH·3.5H2O and the composition of the mother liquor in the NaOH-KOH-NaCl-KCl-H2O system, which was necessary for recovering potassium from the caustic solution containing chlorides by crystallizing NaOH·3.5H2O.
The triple (saturating) point with NaOH·3.5H2O, NaCl, and KCl crystals was found to be 11.94°C where the mole ratio of sodium ion to the total positive ions and that of hydroxide ion to the total negative ions were 0.930 and 0.952, respectively. When the mole ratio of sodium ion was larger than 0.930, NaCl and NaOH·3, 5H2O were crystallized, but KCl and NaOH·3.5H2O when it was smaller than 0.930.
