Effervescent products aqueous solubility

G RBON DIOXIDE is well known as a nontoxic gas that is present in the normal atmosphere at concentrations of about 330 parts per million (ppm). It is also familiar as a chief product of combustion of coal and hydrocarbons. C02 is soluble enough in water and aqueous mixtures to be useful in providing effervescence to a multitude of drinkable products. However, at pressures high enough to liquefy it (the critical temperature, pressure, and density constants of C02 are respectively, Tc = 31.04 °C or 87.87 °F, Pc = 72.85 std atm or 1070 psia or 7.381 MPa, pc = 0.468 g/cm3 or 29.22 lb/cu ft), its properties render it useful for another purpose as well. 

Sodium hydride (3 equiv per H to be replaced) is added to a solution of the substrate (substrate solvent ratio 1 20, w/v) contained in a small flask, which is then protected from atmospheric moisture and CO2 with a KOH drying tube. The flask is shaken occasionally and, when effervescence ceases, the halide (2 equiv per H to be replaced) is introduced with stirring, which is continued for 15-60 min. When the reaction is complete, the excess of the etherification reagents is destroyed by the addition of methanol, and the mixture is ready for chromatographic analysis. Alternatively, the mixture is diluted with water and the organic solvents are removed with a rotary evaporator, whereupon the solid product often separates. It is filtered off and dissolved in dichloromethane, and the dichloromethane solution is washed in a separatory funnel with water until neutral. The product is isolated by concentration of the organic phase (dried over anhydrous calcium chloride or sodium sulfate). For water-soluble substances, the aqueous phase obtained... 

---