Abstract: A method for preparing 2-pyrazolin-5-ones from 1,2,4-oxadiazoles is described. The method comprises forming a liquid reaction system of a base catalyst and a 1,2,4-oxadiazole in an organic liquid reaction medium and heating the reaction system to a temperature sufficient to cause the 1,2,4-oxadiazole to be rearranged to a 2-pyrazolin-5-one.

Abstract: A method for recovering a metal from a solution containing ions of the metal and a complexing agent for the ions is disclosed. The method involves contacting the solution with another metal more electropositive than the metal to be recovered in order to bring about a metal-metal exchange reaction which will yield a precipitate of the metal to be recovered. The precipitate is then separated from the solution. In order to maximize the yield of the metal-metal exchange reaction, the redox potential of the solution is measured during the course of the reaction, and the precipitate is separated from the solution as soon as the redox potential substantially reaches a predetermined minimum value.

Abstract: A method is disclosed for alleviating the partial inactivation of color couplers caused by adventitious reaction with vapors of formaldehyde or a vinyl monomer. Partial inactivation is evidenced by decreased spectral absorptivity of the dye produced by reaction of the color coupler with color dye-forming compounds, such as oxidized photographic color developing agents. The method comprises contacting a partially inactivated coupler with an aqueous solution comprising an oxidizing agent and an oxidation accelerator.