Experiments on animo-acids

This method has been shown by du Vigneaud & Meyer [1932] to cause very little racemization. The molecular proportions used by these authors were employed in each preparation, unless otherwise stated, and the yields obtained were uniformly good. After adding H2SO4 exactly equivalent to the NaOH employed in the preparation, the product was separated, from the resulting Na2SO4 by extraction with hot alcohol. After evaporation of the alcohol in vacuo, the product was recrystallized from a suitable solvent, as described below. The acid equivalent weights of the compounds were determined by titration against a standard NaOH solution, using phenol red as indicator.