Heat measurements applied to biochemical analysis: glucose in human serum.

d-(?)-Arginine was isolated by fractionally recrystallizing dl-arginine-l_s-(?)-malate to obtain the less soluble d-(?)-arginine-l_s-(?)-malate, then passing aqueous solutions of the latter through ionic resin columns to separate the d-arginine from the malic acid. The d-arginine was converted to the monohydrochloride. The fractional crystallization readily yielded 51–73% of the d-arginine-l-malate. d-Arginine monohydrochloride was obtained from the latter in yields of 74–83% of the theoretical.Impure l-arginine was separated from the more soluble arginine malate residues. Two methods of racemizing it for recycling were tested. The separated malic acid was evaporated to dryness in vacuo for reuse, or precipitated as the calcium salt.