191, 192. ASPARAGINE; GLUTAMINE; LEUCINE. 207 



asparagine, and melt at 100 to a homogeneous mass easily soluble 

 in water. Should the addition of alcohol not be followed by the 

 immediate formation of crystals, Borodin recommends covering 

 the object with a coverslip, allowing the spirit to evaporate, and 

 then again looking for crystals. 



Schulze and Ulrich detected glutamine in beet-juice by precipi- 

 tating with a slight excess of basic acetate of lead and filtering. 

 To the filtrate which contains the glutamine, hydrochloric acid is 

 added in the proportion of 25 cc. to a litre ; on boiling for two 

 hours the glutamine is decomposed, like asparagine, into ammonia 

 and the corresponding acid (glutamic acid). The greater part of 

 the hydrochloric acid is now removed by concentrated solution 

 of acetate of lead, and to the filtrate basic acetate of lead is 

 added until the precipitate first formed is redissolved, with the 

 exception of the remainder of the chloride of lead. The lead 

 salt of glutamic acid is then precipitated from the filtered solu- 

 tion by the addition of alcohol. It is collected, decomposed 

 with sulphuretted hydrogen, and filtered from the sulphide of 

 lead. After expelling the excess of sulphuretted hydrogen 

 from the liquid, oxide of silver is added to remove any hydro- 

 chloric acid present, the solution freed from silver by sulphuretted 

 hydrogen, and evaporated to crystallization. The glutamic acid 

 thus obtained may be purified by conversion into a copper salt 

 and regeneration by sulphuretted hydrogen. The presence of 

 glutamic acid was confirmed by converting with nitrous acid into 

 the corresponding oxy-acid, from which pyrotartaric acid was 

 obtained by the action of hydriodic acid. 



The last portion of glutamic acid from the crystallization of 

 the crude product was found to contain aspartic acid. 1 



Glutamine may be estimated quantitatively in the same manner 

 as asparagine. 



For the quantitative determination of asparagine, leucine, tyrosine, 

 etc., see also 241. 



192. Leucine. This substance has also been detected in 

 certain plants. 2 It may be separated from albuminous substances 

 by dialysis, and if present in solution with asparagine, will be 

 found in the mother-liquor after the crystallization of the latter. 



1 Compare Zeitschr. f. anal. Chem. xvii. 104, 1878. 



2 Compare, for instance, Gorup Besanez, Ber. d. d. chem. Ges. vii. 146, 

 569, 1874 (Journ. Chem. Soc. xxvii. 494). 



