Abstract: A process for resolving a racemic modification of .beta.-adrenergic aryl- or hetaryl-oxypropanolamines such as (.+-.)-2-[2-hydroxy-3-[[2-(1H-indol-3-yl)-)-1,1-dimethylethyl]amino]propox y]benzonitrile into its individual enantiomers is described. The process comprises converting the racemic modification into a pair of diastereomeric urea derivativesby reaction with a chiral aralkylisocyanate; separation into the individual diastereomers; and facile regeneration of the starting amine by cleavage of the intermediate urea compound using hydrazine. This final step is improved by the addition of an .alpha.-keto carboxylic acid, such as pyruvic acid, which functions as a scavenger of nucleophilic by-products.

Abstract: Methods are provided for recovering biuret from aqueous urea solutions and for producing relatively concentrated biuret-containing extracts which involve contacting a biuret-containing aqueous urea solution with the hydroxide ion form of an anion exchanger to retain at least a portion of the biuret on the exchanger, contacting the resulting biuret-containing ion exchanger with an aqueous extractant under conditions sufficient to form a biuret-containing extract, and contacting the resulting biuret-containing extract with the same or other biuret-containing anion exchanger in the same or subsequent cycles under conditions sufficient to increase the biuret concentration of the extract. The biuret-containing urea feed solution may also contain higher molecular weight urea condensation products, and the biuret can be selectively separated from such condensation products by the disclosed methods.