Influence of Additives on the Width of the Metastable Zone

Abstract

The width of metastable zone of unseeded potassium alum solutions was determined for different conditions and in the presence of additives. The measurements were taken at three different cooling rates and for three different saturation temperatures at a cooling rate of 10 K/h by means of an ultrasonic measuring technique. The influence of Cr 3+ , Cu 2+ , and Mg 2+ ions on the width of metastable zone of a potassium alum solution was investigated at a cooling rate of 5 K/h. The influence of Mg 2+ ions on the width of metastable zone of potassium chloride solutions was also investigated at a cooling rate of 10 K/h. Cr 3+ , Cu 2+ , and Mg 2+ ions show both enlargement and suppression effects on the width of metastable zone of potassium alum and potassium chloride solutions depending on their concentrations. Cr 3+ , Cu 2+ , and Mg 2+ ions also change the saturation temperature of potassium alum solutions depending on their concentrations.

Water-Pathway Sealing by Crystallization under Advective Supersaturated Solution Conditions

“…However, if the supersaturation level and rapid cooling rate can be controlled, spontaneous nucleation is limited. 12) Comparing the cooling rate in this study with the data of Titiz-Sargut and Ulrich, 12) the cooling rate in this study corresponds to a rapid case, so it was expected that the cooling rate used in our experiment would suppress spontaneous nucleation in the aqueous solution. The growth of K-alum in aqueous solutions in the reaction cell was experimentally observed using a stereoscopic microscope.…”

Effects of impurity ions on solubility and metastable zone width of phosphoric acid

“…Thus, in our case, the apparent secondary nucleation order of phosphoric acid is 3.50. It is well known that impurity ions doped in saturated solution have a significant influence on crystallization process [9,11]. In this article the role of Fe 2+ and SO 4 2-in about 80 -91 wt % phosphoric acid solutions was investigated in detail.…”

“…In this study the polythermal method is more appropriate for solubility measurement. As reported in many literatures [9][10][11], traces of impurities (<100 ppm Cr 3+ ) [3] have dramatic effects on both solubility and MZW. In this study, typical impurity ions as Fe 2+ and SO 4 2-were added into phosphoric acid and the effects were investigated in details too.…”

Influence of Trivalent Metal Ions on the Metastable Zone Width of Ammonium Sulfate

“…However, if once a suitable experimental setup is established to measure the MZW, reproducible and reliable results can be obtained as in the case of the ultrasonic speed measurement. This method was already successfully applied in several publications [5,7].…”

“…The adsorbed amount of Fe 3+ increased with increasing pH value, which stands in contradiction to a decreasing impurity effect with increasing pH value. Therefore, they assumed that the first two hydrolysis products adsorb at the surface of potassium sulfate but only one of them is growth suppression-active, in this case the first hydrolysis product [Fe(H 2 O) 5 …”