Method for Rapid Determination of Specific Gravity

Abstract

The method here described is a simplification of that developed by LINDERSTRBM-LANG and LANZ (1938). Principle.A reasonably linear specific gravity gradient is produced in a vertical measuring cylinder (200 cc) by mixing kerosene and bromobenzene in varying proportions. If a drop of a given solution is introduced under the surface, it will fall with diminishing velocity and finally come to rest a t a position in the cylinder where the specific gravity of the kerosene-bromobenzene mixture is equal to that of the drop in question.Before introducing the drop of the solution under investigation, other drops (standard drops) are introduced of potassium chloride solutions of accurately known specific gravity. NaturaUy these drops will also come to rest a t levels where their specific gravities are equal t o that of the surrounding medium. Plotting the positions of the potassium chloride drops as ordinates against the corresponding specific gravities as abscissae, a reasonably straight line is obtained in the coordinate system, from which it is possible, knowing the position of the drop of the unknown solution, to read the specific gravity of this solution with considerable accuracy. The specific gravity may also be calculated by linear interpolation.This simple principle is known from the above quoted paper by LINDERSTR0M-LANG and LANZ.

Density Gradient Techniques.

“…When an ion or an ion dipole is produced, the aqueous solution contracts due to hydration of the ions with a local destruction of the open structure of liquid water (9, 20). This effect has been utilized to follow the enzymatic hydrolysis of polypeptides by means of the density gradient column (49,51,42,38). When a peptide bond is broken in water there is an increase in density due to electrostriction by the carboxyl and amino groups which is far in excess of the increased molal volume expected for the breakage of the bond.…”

“…Fick (26) in 1855 demonstrated experimentally that if two miscible liquids which are contained in different reservoirs are allowed to interdiffuse, then eventually a linear density gradient is set up in the tube connecting the two reservoirs. Linderstr0m-Lang around 1936 (52,49,51,42,38) revived interest in the density gradient column and demonstrated its potentialities for certain chemical reactions. Recently, particularly due to the effects of Meselson, Vinograd and others (60,59, 34), a new density gradient technique has been applied in the ultracentrifugation of macromolecules, wherein the gradient (usually of aqueous CsCl) is actually produced by the centrifugal field.…”

The Effect of Testosterone and Allied Compounds on the Mineral, Nitrogen, and Carbohydrate Metabolism of a Girl With Addison's Disease 12

“…This fall was associated with a diminution in urinary potassium and in both total and urea urine nitrogen excretion. Withdrawal of the testosterone therapy (periods 16,19) resulted in a rise of the serum potassium to within normal limits (3.5 to 5.0 m.eq. per liter) and an increase in urinary potassium and total and urea nitrogen excretion.…”