THE ISOLATION OF AMINO ACIDS FROM MIXTURES AS THEIR N-2,4-DINITROPHENYL DERIVATIVES, METHIONINE, LEUCINE, PHENYLALANINE, ORNITHINE, LYSINE AND TYROSINE.

1. The separation of the dinitrophenyl derivatives of methionine, leucine (together with isoleucine), phenylalanine, ornithine, lysine and tyrosine from each other, and from the dinitrophenyl derivatives of the other protein amino acids, by partition chromatography on columns is described. 2. The harmful effect on resolving power of using too close-fitting a packing tool in preparing these partition columns is indicated and the dimensions needed to obtain good resolution are given.