Still, Othmer recirculation

Vapor-liquid equilibrium experiments were performed with an improved Othmer recirculation still as modified by Johnson and Furter (2). Temperatures were measured with Fisher thermometers calibrated against boiling points of known solutions. Equilibrium compositions were determined with a vapor fractometer using a type W column and a thermal conductivity detector. The liquid samples were distilled to remove the salt before analysis with the gas chromatograph the amount of salt present was calculated from the molality and the amount of solvent 2 present. Temperature measurements were accurate to 0.2°C while compositions were found to be accurate to 1% over most of the composition range. The system pressure was maintained at 1 atm. 1 mm... 

The data were obtained by means of an improved Othmer recirculation still (34), as modified for salt effect studies by Johnson and Furter (22,35). Thermal energy was applied to the still by means of a heating mantle controlled by a rheostat in order that the boiling rate could be adjusted effectively. Suppression of bumping of the solution and both thermal and physical homogeneity were maintained by means of a magnetic stirring mechanism. 

Donald F. Othmer while at Eastman Kodak during the 1920 s experimented using salts to concentrate acetic acid (14). He also developed an industrial process for distilling acetone from its azeotrope with methanol by passing a concentrated calcium chloride brine down the rectification column (15). Pure acetone was condensed overhead, and acetone-free methanol was recovered in a separate still from the brine which was then recycled. The improved Othmer recirculation still (16) has been the apparatus generally favored by investigators who have studied the effects of salts on vapor-liquid equilibrium. 

The apparatus used—the improved Othmer recirculation still modified for salt effect studies—was described previously (1,7), as were the analytical techniques, specifications on the purity and treatment of the solvents, and details of surface tension and solubility measurements (4). 

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