Growth of Single Crystals of NaH_2PO_4 (NaDP), NaH_2PO_4·H_2O (NaDP·H_2O), and NaH_2PO_4·2H_2O (NaDP·2H_2O) Sodium Dihydrogenphosphate Based on the Analysis of the Na_2O-P_2O_5-H_2O Phase Diagram

摘要

The crystallization conditions for the NaH_2PO_4, NaH_2PO_4·H_2O, and NaH_2PO_4·2H_2O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na_2O-P_2o_5-H_2O system in the temperature range from 0 to 100 ℃. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H_3PO_4 and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP·H_2O, and NaDP·2H_2O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP·H_2O single crystals are determined.