LEUCINE. 141 



isovaleraldehyde, ammonia, and hydrocyanic acid is optically inactive. 

 Inactive leucine may also be prepared, as shown by E. SCHULZE and 

 BossHARD, 1 by the cleavage of proteins with baryta at 160-180 C., 

 because of a racemation, as the ordinary leucine is racemized on heating 

 with baryta at this temperature. The cW-leucine may be split into 

 the two components by various means, especially by the preparation 

 of the formyl combination. 2 



On oxidation the leucines yield the corresponding oxyacids (leucinic 

 acids). Leucine is decomposed on heating, evolving carbon dioxide, 

 ammonia, and amylamine. On heating with alkalies, as also in putre- 

 faction, it yields valeric acid and ammonia. 



Leucine crystallizes when pure in shining, white, very thin plates, 

 usually forming round knobs or balls, either appearing like hyaline, or 

 with alternating light and dark concentric layers which consist of radial 

 groups of crystals. By slow heating, leucine melts and sublimes into white, 

 woolly flakes, which are similar to sublimed zinc oxide. At the same 

 time an odor of amylamine is developed. Quickly heated in a closed 

 capillary tube, it melts with decomposition at 293-295. 



Leucine, as obtained from animal fluids and tissues is always impure, 

 and is very easily soluble in water and rather easily in alcohol. Pure 

 leucine is soluble with difficulty. Pure I- and d-leucine dissolve in 40- 

 46 parts water, more readily in hot alcohol, but with difficulty in cold 

 alcohol. The d-Z-leucine is much less soluble. According to HABER- 

 MANN and EHRENFELD 3 100 parts of boiling glacial acetic acid dissolve 

 29.23 parts of leucine. The specific rotation of Z-leucine, dissolved in 

 hydrochloric acid (20 per cent solution) is (a) D =+15.6 according to 

 FISCHER and WARBURG. In aqueous solution it is (a) D = 10.42 r 

 according to EHRLICH and WENDEL."* 



The solution of leucine in water is not, as a rule, precipitated by 

 metallic salts. The boiling-hot solution may, however, be precipitated 

 by a boiling-hot solution of copper acetate, and this fact is made use of 

 in separating leucine from other substances. If the solution of leucine 

 is boiled with sugar of lead and then ammonia be added to the cooled 

 solution, shining crystalline leaves of leucine-lead oxide separate. Leucine 

 dissolves cupric hydroxide, but does not reduce on boiling. 



Leucine is readily soluble in alkalies and acids. It gives crystalline 

 compounds with mineral acids. If leucine hydrochloride is boiled with 

 alcohol containing 3-4 per cent HC1, long narrow crystalline prisms of 



1 See Zeitschr. f. physiol. Chem., 9 and 10. 



2 Fischer and Warburg, Ber. d. d. chem. Gesellsch., 88. 



3 Zeitschr. f. physiol. Chem., 37. 



4 Fischer and Warburg, Ber. d. d. chein. Gesellsch., 38; Ehrlich and Wend el, 

 Biochem. Zeitschr., 8. 



