142 THE PROTEIN SUBSTANCES. 



giobin, and FISCHER and DORPINGHATJS 18.3 per cent from horn sub- 

 stance. 1 



The leucine obtained by cleavage of protein substances is generally 

 Z-leucine, which is levorotatory in water solution and dextrorotatory 

 in acid solution. The leucine prepared synthetically by HtiFNER 2 

 from isovaleraldehyde, ammonia, and hydrocyanic acid is optically 

 inactive. Inactive leucine may also be prepared, by the cleavage of pro- 

 teins with baryta at 160-180 C., because of a ready racemation. The 

 d-Z-leucine may be split into the two components by various means, espe- 

 cially by the preparation of the formal combination. 3 



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. On putrefaction it yields 

 isoamylamine and isocaproic acid. 



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 la}'ers 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 eW-leucine is much less soluble. According to HABER- 

 MANN and EnRENFELD 4 100 parts of boiling glacial acetic acid dissolve 

 29.23 parts of leucine. The specific rotation of /-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 = 10.40, 

 according to F. EHRLICH and WENDEL. 5 



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 



1 Erlenmeyer and Schoffer, cited from Maly, Chem. d. Verdauungssafte, in Her- 

 mann's Handb. d. Physiol., 5, Theil 2, p. 209; Fischer and his collaborators, ibid., 36. 



2 Journ. f. prakt. Chem. (N. F.), 1. 



3 Fischer and Warburg, Ber. d. d. chem. Gesellsch., 38. 



4 Zeitschr. f. physiol. Chem., 37. 



5 Fischer and Warburg, Ber. d. d. chem. Gesellsch., 38; E. Ehrlich and Wendel, 

 Biochem. Zeitschr., 8. 



