Calcite is one of the anhydrous polymorphs of calcium carbonate. When it is found in biominerals, they often have complex morphologies controlled by associated proteins. Asprich, rich in carboxylic acid groups, is one of the representative proteins. In previous studies, peptides originated from Asprich showed extensive modification abilities of calcite morphologies, especially in the presence of magnesium ions. In the present study, synthetic polymers with carboxylic acid groups were utilized to regulate the morphologies of calcite. Poly(acrylic acid) and poly(methacrylic acid) were able to reproduce the controlling ability of Asprich peptides, but poly(ethylene imine) and poly(N-isopropylacrylamide) could not. The observed phenomenon can be explained through selective binding of the anionic polymers to the {hk0} planes of calcite.

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Sodium hydroxide solutions are often employed as sterilization agents in the pharmaceutical industry. Here, the chloride content is considered as a critical impurity. In this study, an electrochemical method was developed to remove chloride ions (Cl¯) through the oxidative deposition of AgCl on a Ag anode. The Cl¯ content in the commercially available 50% w/w NaOH solution employed was approximately 100 mg Cl¯/kg NaOH. As the OH¯ content is approximately 18,000 times higher than the Cl¯ content, the formation of AgCl may be expected to be thermodynamically less favorable than the formation of Ag 2 O. However, activation energies for AgCl and Ag 2 O formation have been reported to be approximately 3.8 and 31.2 kJ/mol, respectively, and indicate that AgCl formation is favored. AgCl can be selectively produced by controlling the anode potential. Here, the Cl¯ concentration was reduced to less than 50 mg Cl¯/kg NaOH when an anode potential of 0.18 or 0.19 V vs. Hg/HgO (reference electrode) was applied for one hour at 50°C. XRD analysis and visual monitoring of the Ag anode confirmed the oxidative deposition of AgCl on the anode surface as well as the electrochemical desalination of the concentrated NaOH solution.

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) particles were prepared through solvent-antisolvent crystallization at room temperature by using dimethyl sulfoxide and ethanol as a solvent and an antisolvent, respectively. Estane, which has been used as a polymer binder in polymer-bound explosives, was added to retard nucleation and inhibit crystal growth. The particles were characterized using scanning electron microscopy, X-ray diffraction analysis, nuclear magnetic resonance spectro-scopy, and thermogravimetric analysis. Owing to the nucleation at a high degree of supersaturation, thermodynamically unstable submicron non-β-form HMX particles were formed initially. Their morphology was changed to β-form; the submicron size was maintained while the particles were entrapped in Estane. Estane was removed by washing with tetrahydrofuran, and the purity of the submicron β-form HMX particles was greater than 99 %.