A process was developed for dehydrating aqueous solutions of hydrazine by azeotropic distillation with aniline as an entrainer. The ternary system hydrazinewater-aniline, which contains the minimum-boiling aniline-water azeotrope and the maximum-boiling hydrazine-water azeotrope, was studied by fractionation analysis to determine the position of the ridge or distillation barrier in the vapor and liquid surface. The studies showed that the position and curvature of this ridge were favorable for the production, by rectification, of a solution richer in hydrazine than the azeotropic proportions. The process comprised three operations. Approximately 70% of the hydrazine charged to the system was dehydrated.Entrainers that form binary minimum-boiling azeotropes with both hydrazine and water are discussed. Ternary systems with these entrainers have saddlepoint azeotropes that boil intermediate with respect to the other invariant components in the system.Hydrazine is currently being produced by modifications of the German Raschig process, in which it is obtained in a low-concentration ( 1 to 3 % ) aqueous solution (1). Because of the maximum-boiling hydrazine-water azeotrope, sometimes called hydrazine hydrate, conventional distillation methods cannot be used to concentrate this solution to more than about 70 wt. % hydrazine and 30% water. ( 6 ) . In the past, anhydrous hydrazine has been produced chemically through ithe formation of inorganic or organic derivatives which must be subjected to further treatment to yield the dehydrated product ( 2 ) . Since these methods are costly, exploratory work was undertaken t o determine whether an aqueous hydrazine solution could be dehydrated by distilling the solution in the presence of a third component that formed a minimumboiling azeotrope with water. Of t h e numerous materials tested initially, aniline was the first to show real promise as an effective entrainer, and the process described is based on its use. THE HYDRAZINE-WATER-ANILINE SYSTEMThe ternary system hydrazinewater-aniline was studied by fractionation analysis t o determine the principal features of the vaporliquid equilibrium surfaces. The basic principle of this method is t h a t when an invariant component, i.e., a pure compound or azeotrope, is distilled from a mixture, the composition of the remaining solution moves rectilinearly in the opposite direction from the invariant component. This method was used by Ewe11 and Welch ( 3 ) for studying ternary systems with binary azeotropes, and by Lecat(4) for determining the composition of azeotropes in binary systems. The Todd precise fractionation assembly was used for the present analysis.The Todd fractionating column consisted of a 1/2-in. glass column packed %-in. high with 1116411. glass helices. The pot had an opening for a standard-taper thermometer and one for the entrance of nitrogen. All the vapors were condensed in the column head and the reffux was varied by adjusting a valve on the take-off line. Rubber tubing connecting the receiver vent to a bubbler ...

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search Triangle Park, NC 27711, under Grant USEPA CR807558, and the American Iron and Steel Institute, Washington, DC,

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Prior to 1972, polychlorinated biphenyls (PCBs) were widely used as a fire-retardant additive in hydraulic oils employed in foundry die-casting machines. When the sale of hydraulic fluids containing PCBs for non-closed-loop applications was stopped in 1972, existing PCB-laden hydraulic oil stocks were recycled with losses replaced with PCB-free hydraulic oils containing an alternate phos hate to recycle oils containing more than 50 ppm PCBs contaniinated oils were removed from foundry operations and stored. However, a common problem experienced by