206 THE PRODUCTS OF ALBUMINOUS DIGESTION. 



In absolute alcohol it is insoluble. Its aqueous solutions are laevo- 

 rotatory, while in the presence of nitric acid dextrorotatiou is 

 observed. 



As has been shown (page 81), aspartic acid is a dibasic acid 

 of the fatty series. It is amido-succinic acid, and is represented by 

 the formula CH 2 .CH(NH 2 ).(COOH) 2 . It can be obtained from 

 asparagin on boiling with hydrochloric acid, as shown in the 

 equation : 



CH 2 .CONH 2 CH 2 . COOH 



| + H 2 0=I +NH 3 . 



CH(NH 2 ).COOH CH(NH 2 ).COOH 



Asparagin. Aspartic acid. 



It has also been produced synthetically. On reduction it yields 

 succinic acid. 



With cupric oxide aspartic acid forms a crystalline compound 

 which is almost insoluble in cold water, but dissolves in boiling 

 water with comparative ease. This property is utilized for the pur- 

 pose of isolating the substance from the mixture of digestive products. 



Glutaminic Acid. Glutaminic acid is one of the most constant 

 decomposition-products of the proteins and found in especially 

 large amounts in the vegetable albumins, where its amide glutamin 

 also plays a very important rdle. The largest quantities have 

 been obtained from the gliadin of wheaten flour (31.5 per cent.), 

 zein, and edestin. In the albuminoids the amount is relatively 

 small and in silk fibrin it seems to be absent. Kutscher claims to 

 have found it in the so-called antipeptone of Kiihne, which was 

 obtained from fibrin. It is noteworthy that much larger quantities 

 are found if the decomposition of the albumins is effected with 

 hydrochloric acid than with sulphuric acid. Kutscher thus found 

 only 1.8 per cent, among the decomposition-products of casein 

 when using sulphuric acid, while Hlasiwez and Habermann obtained 

 as much as 29 per cent, when hydrochloric acid was used. 



Glutaminic acid crystallizes in small glistening crystals, which 

 are soluble with difficulty in cold water, while in boiling water they 

 dissolve with greater ease, but separate out on cooling. With acids 

 and alkalies it combines to form salt-like products, among which 

 the hydrochiorate is conveniently utilized for the purpose of iden- 

 tifying the substance. The melting-point of this compound is 

 193 C. 



The composition of glutaminic acid is expressed by the formula 

 CH 2 .CH 2 .CH(NH 2 ).(COOH) 2 . It is thus amino-glutaric acid, and 

 bears the same relation to glutamin as that which exists between 

 aspartic acid and asparagin. This is represented in the equation : 



/CONH, /COOH 



CH 2 .CH 2 .CH(NH 2 )< + H 2 O = CH 2 .CH 2 .CH(NH 2 )< - 



\COOH \COOH 



Crlutamin, Glutaminic acicj. 



