CHAP. III.] GLUTAMIC ACID. 253 



liquor in which the acid is suspected to exist is saturated with 

 gaseous HC1,- at the temperature of C. and is placed in a freezing 

 mixture for some hours. The' HCl-salt crystallises in the form of 

 large triclinic tables and prisms, which have the composition 

 C 6 H 9 NO 4 + HC1, which are very sparingly soluble in cold HC1, and 

 very soluble in water. To obtain glutamic acid from this compound, 

 the latter is dissolved in hot water, and to the boiling solution 

 freshly precipitated moist silver oxide is added as long as a precipi- 

 tate of chloride of silver separates. The filtrate from the precipitate 

 is treated with H 2 S, decolourised, concentrated, and set aside for 

 some days to crystallise 1 . 



Physical and Chemical Properties. 



Glutamic acid crystallises in the form of small plates or of 

 rhombic tetrahedra or octahedra. It is insoluble in alcohol or ether, 

 and is sparingly soluble in cold yater (at 16 C., 1 part is soluble in 

 100 parts of water). Its melting point is 135 140. Even dilute 

 solutions reduce Fehling's solution. 



Rotatory Aqueous and acid solutions of glutamic acid are 



power. dextro-rotatory. In the case of a dilute hydrochloric 

 acid solution containing 9'0 grammes of HC1, and 5 grammes of 

 glutamic acid in 100 C.C., the specific rotatory power (a) D = + 31*1 

 to 31-6 (Schulze and Bosshard). 



In the case of glutamic acid, as in that of leucine, Schultze and 

 Bosshard found that the dextrogyrous body, by long heating with 

 barium hydrate at 150 160, yielded an inactive body of the same 

 composition. Here, again, by sewing Penicillium glaucum in an 

 appropriate nutrient sterilised medium to which the inactive 

 body had been added, they succeeded in obtaining an optically 

 active amido-acid, which, however, instead of being dextrogyrous, 

 as the normal acid, is Isevogyrous. Under the conditions of acidity 

 and temperature previously referred to, the laevorotatory power of 

 this glutamic acid (a) D = - 33 3 to - 33'2. 



The slight difference between the rotation of the plan of polarisa- 

 tion of the dextro- and the laevo-gyrous bodies depends doubtless 

 upon slight and unavoidable impurities. 



The Cu-compound of glutamic acid obtained by boiling it with 

 freshly precipitated Cu(OH) 2 separates in the form of prisms, having 

 the colour of lapis lazuli, and the composition C 5 H 7 NO 4 Cu -f 2H 2 O 

 (Ritthausen, Franz Hofmeister). This salt is soluble in about 3400 

 parts of cold and 400 parts of boiling water. 



1 Karl B. Hofmann, Lehrbuch der Zoochemie, Wien, 1879, pp. 635637. 



