100 LEUCIN AND TYROSIN REATIONS. 



can be filtered off, while the leucin remains in solution. Remove 

 the lead from the filtrate which contains the tyrosin by passing 

 hydrogen sulphid through it, filter, and concentrate the filtrate, 

 then boil it with freshly-prepared copper oxyhydrate. (This is 

 made by precipitating a solution of copper sulphate with sodium 

 hydrate and washing by decantation until it no longer has an 

 alkaline reaction.) Part of the leucin is thrown down as the copper 

 salt and a part remains in solution. The precipitate can be re- 

 moved by filtration and the leucin obtained in the pure state by 

 removing the copper by hydrogen sulphid and allowing the leucin 

 to crystallize after concentration. From the deep-blue filtrate the 

 copper salt can be obtained by evaporating it to a small volume 

 and letting it crystallize. It forms sky-blue aggregations of 

 crystals. If desired, the copper can be removed from these also 

 by hydrogen sulphid. The leucin thus obtained is not as pure as 

 the first portion. 



217. Test the tyrosin with Millon's reagent. It gives a red 

 color, showing the presence in the molecule of the group C H 4 OH. 

 (Hoffman's test.) 



218. To a portion of tyrosin crystals as large as half a pea 

 add, in a porcelain dish, a few drops of concentrated sulphuric 

 acid and warm on the water-bath. This forms tyrosin sulphuric 

 acid. This is diluted with water and enough barium carbonate 

 added to neutralize it, then filtered. The filtrate contains the 

 tyrosin compound, which, with a very dilute solution of ferric 

 chlorid, gives a deep-violet solution of tyrosin ferric sulphate. 

 (Piria's test.) 



219. Warm the tyrosin with a mixture of formalin, 1 part; 

 water, 45 parts: concentrated sulphuric acid, 55 parts. An 

 emerald green color results. (Morner's test.) 



220. Evaporate a small portion of the leucin crystals with a 

 drop of nitric acid upon platinum foil. The residue is colorless, 

 but on adding a drop of sodium hydrate becomes yellow to brown, 

 and on gently heating rolls around on the foil in the form of 

 drops. (Scherer's test.) 



221. Place a few crystals of leucin in a dry test-tube and 

 heat gently. They melt with the odor of amylamin and sublime, 

 the leucin appearing on the sides of the tube as wooly flakes. 

 This may not succeed if the leucin is very impure. 



