112 



Scientific Proceedings (49). 



which picrolonates were prepared, after each being given the solu- 

 bility of the picrolonate in grams per 100 c.c. of water at 20°-23°, 

 and the melting point. The picrolonates are arranged in order of 

 solubility. Dl-phenyl-alanine, 0.12, 212 0 (decomp.); Tyrosine, 

 0.29, blackens at 260 0 ; l-phenyl-alanine, 0.34, 208 0 ; dl-leucine, 

 0.53, indefinite above 140 0 ; l-leucine, 0.55, indefinite at about 150 0 ; 

 d-isoleucine, 0.58, 170 0 ; dl-valine, 0.81, indefinite above 150 0 ; 

 dl-serine, 0.98, decomposed 265 0 ; glycocoll, 0.99, 214 0 ; dl-alanine, 

 1.01, 216 0 ; d-valine, 1.20, 180 0 ; d-alanine, 1.61, 214 0 ; dl-aspartic 

 acid, 1.69, blackens at 130 0 ; dl-glutaminic acid, 2.37, 194 0 . 



Nearly all the picrolonates decompose more or less on melting, 

 and the melting points are not sharp. L-Phenyl-alanine picrolo- 

 nate is much more soluble in alcohol than the racemic salt, and can 

 be separated from most of the racemic substance by solution in 

 alcohol. The optically active compound has a sp. rotation in 

 absolute alcohol of + 30 0 . The specific rotation of d-isoleucine 

 picrolonate in alcohol is + 33. 3 0 . Phenyl-alanine can be sepa- 

 rated from glutaminic or aspartic acid by dissolving the mixture 

 with enough picrolonic acid to combine with the phenyl-alanine 

 only. The picrolonate of the latter crystallizes pure. It is prob- 

 able that other amino acids can be separated by similar use of 

 picrolonic acid. The pyrrolidine acids, proline and oxyproline, 

 do not readily yield picrolonates when treated as described above. 



80 (689) 



An improved apparatus for gasometric determination of amino 



nitrogen. 



By DONALD D. VAN SLYKE. 



[From the Rockefeller Institute for Medical Research, New York.) 



The apparatus differs from that reported at the meeting of this 

 society in December, 1909, in that: (1) The desamidizing bottle 

 with stopper holding the 10 c.c. burette and tubes is replaced by a 

 bulb into which the tubes and burette are sealed ; (2) the Hempel 

 absorption pipette is modified so that it can be suspended from 

 hooks; (3) both absorption pipette and desamidizing bulb are so 

 arranged that they can be shaken by a motor. The apparatus, 



