Dyson Rose

Effect of freezing on the pH and composition of sodium and potassium phosphate solutions: the reciprocal system KH2PO4Na2HPO4H2O

Abstract Changes in composition caused by ice precipitation and by salt precipitation affected the pH of solutions of mono- and disodium and potassium phosphates markedly during freezing. Except for neutral and alkaline solutions with a relatively high potassium phosphate content, the pH decreased with temperature during the precipitation of ice alone. Precipitation of dibasic salts was accompanied by a decrease in pH, while precipitation of monobasic salts increased the pH. The effect of simultaneous precipitation of two salts on pH depended on the type of salts precipitating as well as the initial pH. Simultaneous precipitation of disodium and monopotassium phosphates and ice occurred over a wide range of pH and solution composition; it increased the pH of the more alkaline solutions but decreased the pH of acid solutions. Simultaneous precipitation of other two-salt combinations occurred over a rather limited range of pH and composition, and consequently the effect on pH was relatively small. The data obtained provide a relatively complete picture of the phase relations in aqueous solutions of mono- and disodium and potassium phosphates in the freezing zone. The system has eleven eutectic points at temperatures between −0.5 °C. and −17.2 °C.; the pH of the eutectic solutions ranges from 3.3 to 9.3.

Determination of cyanate, and a study of its accumulation in aqueous solutions of urea☆

Abstract Cyanate accumulation in aqueous solutions of urea was measured by means of a spectrophotometric method of improved sensitivity. At 25°C, cyanate accumulation initially occurred at a rate of ca. 0.07 mmole of NCO/liter/day/mole of urea, but the rate of accumulation decreased progressively (especially at higher urea concentrations) and a maximum cyanate level was reached in about 60 days. At a given urea concentration, the maximum cyanate level at 25° was ca. 60% of that obtainable at 38° (7 days), and ca. 23% of that obtained at 85° (50 min). The presence of traces of ammonia in some lots of reagent-grade urea is believed to stimulate initial cyanate accumulation. Cyanate accumulation was prevented by storage of neutral solutions of urea (prepared at temperatures not exceeding 25°) at 5°, or by buffering the urea solutions at pH 4.7.

Effect of magnesium on formation of calcium phosphate precipitates.

Abstract The effect of magnesium on the precipitation of gelatinous granular, and “total” calcium phosphates was studied with 1–8 mmoles magnesium/l. Precipitation of these salts was induced by adding dilute sodium hydroxide to the aqueous solutions. Gelatinous calcium phosphate contained less magnesium after suspension in magnesium solutions than, when precipitated in the presence of magnesium. It is concluded that Mg++ ion (or MgOH+) competes with Ca++ ion (or CaOH+) for exchange with H+ ion of the gelatinous precipitate, and that the greater retention of magnesium obtained by precipitation can be ascribed to lattice incorporation. Granular calcium phosphate did not contain magnesium when precipitated in the presence of magnesium; however, dicalcium phosphate was present in this precipitate, associated in various proportions with granular salt. It appears that the presence of magnesium decreases the rate of conversion of dicalcium phosphate into the more alkaline granular precipitate, resulting in Ca/P ratios closer to those of dicalcium phosphate. “Total” calcium phosphate obtained in the presence of magnesium could be either granular precipitate or dicalcium phosphate (or mixtures of the two), whereas, in the absence of magnesium, a mixture of gelatinous and granular precipitates was obtained. The disappearance of magnesium from the precipitate during the formation of “total” precipitate was gradual, indicating that gelatinous precipitate was dissolving during precipitation of dicalcium phosphate and conversion of the latter to granular precipitate. The solubility product (pkf) of gelatinous precipitate increased, whereas that of granular precipitate decreased, as the magnesium concentration of the solution was increased.

Effect of rate of ice-crystal on hemolysis of erythrocytes.

Abstract Freezing of washed porcine erythrocytes suspended in various concentrations of glycerol indicated that the protective action of glycerol against hemolysis involves retardation of the rate of ice-crystal growth as well as reduction of salt damage. Possible mechanisms that make slow rate of ice-crystal growth desirable are discussed.