350 TYROSIN. 



which crystallizes in easily decomposable needles with 

 one and a half moleclues water of crystallization. 



Tyrosin, C 9 H n ]TO 3 (perhaps ethylamidoparaoxyben- 

 zoic acid == C 6 H 3 (NHC 2 H 5 ) | QQ QH ) Is produced, 



together with leucine (p. 98) and other products, hy 

 continued boiling of albuminous substances, born, etc., 

 with hydrochloric acid or dilute sulphuric acid, and by 

 fusing them with potassium hydroxide. It also occurs 

 in the living organism, particularly in a diseased con- 

 dition of the organism. It is prepared most advan- 

 tageously from horn, which, in the form of shavings, 

 is kept boiling, for about sixteen hours, with double 

 its weight of concentrated sulphuric acid, previously 

 diluted with from four to four and a half times its 

 volume of water. During the boiling the evaporated 

 water is replaced, the original volume being retained. 

 At the end of the time mentioned the liquid is neutral- 

 ized with milk of lime. The filtered solution is evapo- 

 rated to half its volume, then acidified with sulphuric 

 acid, and, after filtering, mixed with enough white 

 lead to form a thin pasty mass. The solution, which 

 contains the tyrosin, in the form of the lead salt, is 

 treated with sulphuretted hydrogen. On evaporating 

 the filtrate from lead sulphide, the tyrosin crystallizes 

 out, and can be easily obtained in a pure condition by 

 repeated recrystallization. Leucine remains in the 

 mother-liquor. 



Colorless, long, fragile, usually radiating prisms ; 

 very slightly soluble in alcohol, more easily in hot 

 water, insoluble in ether. Combines with bases and 

 acids. When heated alone, it is decomposed and 

 yields phenol and other compounds. When fused with 

 caustic potassa it yields paraoxybenzoic and acetic 

 acids and ammonia. Dilute nitric acid (4 parts water 

 and 4 parts concentrated nitric acid to 1 part tyrosin) 

 converts it, without the aid of heat, into nitrotyrosin 

 nitrate, a crystallizing substance, from the solution of 

 which nitrotyrosin C 9 H 10 (lSr0 2 )N0 3 may be precipitated 

 by ammonia. It crystallizes in thin, pale-yellow nee- 



