200 Hydrolysis of the SolMe Protein of Sivede Turnips 



added. 34-8 c.c. of strong ammonia solution were added and the acids 

 went completely into solution on heating a httle. 55-7 c.c. of 1-1 m. 

 lead acetate solution were added slowly with constant shaking from a 

 burette. The flask was then cooled for an hour under the tap, and the 

 white precipitate of lead leucine filtered off on a Buchner funnel. The 

 mass was well pressed out, washed three times with 90 % alcohol, 

 and finally with ether. It was then dried in a vacuum desiccator. 

 27-23 grms. of lead leucine were obtained equal to 15-28 grms. of leucine 

 or 15-98 grms. after allomng for losses for analyses. 



0-2941 grm. lead leucine gave 0-1910 grm. PbS04 - 0-1304 grm. Pb 



= 44-35 per cent, of lead. 



Calculated for Pb(C6Hi202N)2 = 44-29 per cent, of lead. 



Recovery of the valine. 



The excess of lead acetate was removed from the filtrate by hydrogen 

 sulphide, the lead sulphide filtered off, and the filtrate evaporated to 

 dryness on the water bath. The dry residue in the basin was treated 

 with 3 : 1 alcohol-ether mixture, and washed with it to remove 

 ammonium acetate and acetic acid. The filtrate was evaporated down 

 and retreated to recover the valine dissolved by the first treatment. 

 7-6 grms. of vahne were recovered containing 11-41 % nitrogen showing 

 that some leucine was still left in it. 



15-28 + 7-6 = 22-88 grms. of amino-acids were thus recovered, a 

 loss of only 23-22 — 22-88 = 0-34 grm. having occurred. 



Separation of d-alanine and d-valine. 



A method for the separation of d-alanine and d-vahne has been 

 recently pubhshed by Levene and Van Slyke^ based on the insolubihty 

 of alanine phosphotungstate in 10 per cent, sulphuric acid in the presence 

 of a 20 per cent, excess of phosphotungstic acid. 



Purity of reagents. Because of the large amomits of lead acetate 

 and phosphotimgstic acid used in this method, the authors point out 

 the desirability of using pure chemicals in order to avoid the contamina- 

 tion of the amino-acids with ash. No difficulty was found in obtaining 

 lead acetate by recrystalhsation of sufficient purity ; it gave no residue 

 after precipitation of a solution with hydrogen sulphide and evaporation 

 of the filtrate to dryness. It was found impossible, however, to obtain 

 phosphotungstic acid which gave no residue after precipitation with 



1 Journ. Biol. Chem. xvi, p. 103, 1913. 



