Drift of drops in density gradient columns

Abstract

The rate of drift of drops of sodium chloride solution in density gradient columns composed of mixtures of bromobenzene and kerosine increases with concentration of solute and decreases with drop size. Size also affects position of drop, larger drops tending to come to rest at higher levels than smaller drops. Drift is greatest in columns whose components are dried over calcium chloride, is diminished in columns whose components are presaturated with water or sodium chloride solution, and is nearly eliminated in columns whose components are presaturated with potassium bromide solution. It is not affected significantly by presaturation of aqueous test samples with the mixtures of solvents used in the columns. Drift is also observed with test samples containing solutes other than sodium chloride. Further, it is greater in columns composed of bromobenzene and xylene than in those composed of bromobenzene and kerosine. The significance of these findings as they may affect error of measurement of density is pointed out. A new method for obtaining linearity in density gradient columns also is described.