546 CONSIDERATION OF CARBON COMPOUNDS. 



Leucine, a-amino-caproic acid, CH 3 .(CH 2 ) 3 .OH(NH 2 ).CO 2 H, is widely 

 distributed in small quantity in glands of animals and in the sprouts of plants. 

 It is one of the products of the decomposition of albumins and gelatin (see 

 Index). 



Taurine, Amino-ethyl-sulprionic acid, NH 2 .CH 2 .CH 2 .SO 3 H, is com- 

 bined with cholic acid to form taurocholic acid, which is one of the constitu- 

 ents of bile. It forms very stable monoclinic prisms (see Index). 



Aspartic acid, Amino-succinic acid, C 2 H 3 (NH 2 ).(CO 2 H) 2 , occurs in 

 pumpkin seeds, and is often formed when natural compounds are boiled with 

 dilute acids. In this manner it may be obtained from casein and albumin. It 

 forms prisms difficultly soluble in water. When treated with nitrous acid, it 

 yields malic acid. 



CH 2 .CONH 2 



Asparagine, Amino-succinamic acid, | occurs in 



CH(NH 2 ).CO 2 H, 



asparagus, liquorice, vetches, beans, beets, peas, and in wheat. It forms large 

 crystals, difficultly soluble in cold water. Boiling with acids or alkalies con- 

 verts it into aspartic acid and ammonia. 



Guanidine, (NH)C(NH 2 ) 2 , is obtained by the oxidation of guanine which 

 occurs in guano. Guanine, C 5 H 3 (NH 2 )N 4 O, is the amirio derivative of xan- 

 thine (see Index), which is closely related to uric acid, and which is found in 

 all the tissues of the body and in the urine. Guanidine is an imide of urea, 

 OC(NH 2 ) 2 , is strongly alkaline, and when boiled with dilute sulphuric acid or 

 barium hydroxide solution yields urea and ammonia. 



Creatine, Methyl-guanidine-acetic acid, (HN)C< NG |j Q-^ Q O ,H 



is found in the muscles of all vertebrates, and is closely related to guanidine 

 and to sarcosine. It forms colorless, transparent prisms, soluble in 75 parts 

 of cold water. When evaporated in dilute acid solution, it loses water to 

 form the anhydride, 



NH-CO 



Creatinine, (HN)C\ which forms prisms, readily soluble in 



\NCH 3 -CH 2 , 



water. It is a strong base. It is a constant constituent of urine. Creatine and 

 creatinine are discussed at greater length further on (see Index). 



Urea, Carbamide, CO(NH 2 ) 2 , is the amide of carbonic acid. It occurs 

 in the urine and blood of all mammals, particularly of carnivorous animals. 

 It has been made by various synthetic methods, but is most easily obtained 

 from urine (see Index). It crystallizes in rhombic prisms, melting at 132 C., 

 easily soluble in water and alcohol. When boiled with dilute acids or alka- 

 lies, it yields carbon dioxide and ammonia, thus : 



CO(NH 2 ) 2 + H 2 : C0 2 + 2NH S . 



Urea unites with acids, thus : urea hydrochloride, CO(NH 2 ) 2 .HC1 ; urea ni- 

 trate, CO(NH 2 ) 2 .HNO 3 , which is difficultly soluble in nitric acid; urea phos- 



