80 PROPERTIES OF CERTAIN AMINO-ACIDS. [CH. IV. 



triclinic tables, which melt at about 193. This salt is 

 readily soluble in water, but only very slightly soluble in 

 concentrated hydrochloric acid. The calcium salt is 

 quantitatively precipitated by strong alcohol, provided that 

 the solution be sufficiently concentrated (25 to 30 per cent.). 

 On boiling an aqueous solution of the hydrochloride, it is 

 largely converted into the internal anhydride, pyrollidone 

 carboxylic acid. 



COOH COOH 



CH.NH 2 CH. NH 



CH 2 CH 2 



CH 9 - COOH CH 9 - CO 



H 2 O 



This change does not take place in the presence of strong 

 hydrochloric acid, nor during concentration in vacua at 

 40 to 45. Glutaminic acid is especially abundant in 

 vegetable proteins. It is for this reason that gluten flour, 

 consisting of gliadins and glutelins, is used for its prepara- 

 tion. 



Glutaminic acid is dextrorotatory, [ a ] D in water = + 12. 

 In 10 per cent, hydrochloric acid [ a ] D = + 31.' 



81. Action of nitrous acid. To a solution of glutaminic 

 acid in water add a solution of nitrous acid, obtained by acidifying a 

 strong solution of potassium nitrite with acetic acid. An evolution 

 of nitrogen gas occurs. 



COOH COOH 



CH.NH 2 CH.OH 



CH 2 +HN0 2 CH 2 + N 2 +H 2 



CH 2 .COOH CH 2 .COOH 



Oxy-glutaric Acid. 



