402 STATE BOARD OF AGRICULTURE. 



Copper Salt. — Several hundred milligrams were dissolved in boiling 

 water and the solution saturated with copper carbonate. Carbon dioxide 

 was evolved and the solution turned dark blue. A light blue scum 

 formed on the surface. The solution was filtered hot and concentrated, 

 upon which a dark blue crystalline copper compound separated out. It 

 gave 19.63 per cent copper; calculated for (C«Hi-N0-)2Cu, 19.64 per 

 cent. 



These figures indicated that it might be one of the aminocaproic acids 

 of which leucine is the most prominent. The light blue scum which had 

 been filtered off was dissolved in water, in which it was diflScultlv 

 soluble. Prom this it was evident that the original material contained 

 two compounds, one forming a copper salt easily soluble in water, the 

 other forming a copper salt difficultly soluble in this solvent. As was 

 shown by Ehrlich, such is the case with leucine and isoleucine. His 

 method for separating these two substances was based on the fact that 

 the isoleucine copper salt is readily soluble in cold concentrated methyl 

 alcohol while the corresponding leucine compound is practically insolu- 

 ble. Unfortunately this ideal condition of affairs does not hold abso- 

 lutely when both substances are present. In a mixture of these com- 

 pounds some of the leucine copper salt dissolves in the alcoholic solu- 

 tion of the isoleucine salt while some of the latter is held back in the 

 crystals of the former. For complete purification of the leucine, 

 Ehrlich^ suggested that, after extracting as thoroughly as possible, the 

 leucine copper salt be decomposed with hydrogen sulfide, the copper sul- 

 fide be filtered ofi and the copper salt again formed and extracted as 

 before. Several repetitions of this procedure should remove all of the 

 isoleucine. Recrystallization from water removes the leucine completely 

 from the isoleucine. 



Leucine. — The solution of the mixed copper salts as originally ob- 

 tained was taken to dimness on the steam bath. The resulting light blue, 

 crystalline mass was extracted with small portions of cold concentrated 

 methyl alcohol until the solvent was no longer colored after having 

 been shaken some time with the salt. The solid residue was then dis- 

 solved in water and decomposed with hydrogen sulfide. After filtering 

 off the copper sulfide the solution was saturated with copper carbonate, 

 the excess filtered off and the solution taken to dryness as before. This 

 copper salt was again ext^'acted with methyl alcohol and the process re- 

 peated twice. The last extraction removed only a trace of copper from 

 the solid residue. This was then dissolved in water, and decomposed 

 with hydrogen sulfide. The copper sulfide was filtered off and the solu- 

 tion concentrated. It was levorotatory. The white crystalline sub- 

 stance which separated out gave the following rotation in 20 per cent 

 hydrochloric acid. 



0.0455 gram substance in 11.1373 gram solution (0.4085 per cent; 

 1.086 sp. gr.) gave +0.40° (Ventzke) rot. in a 2 dm. tube at 20°, sodium 

 light. 



[a]J° found = -f 15.62. 



Of) 



[aT Meucene = + 17.3. 



When heated quickly in a capillary tube it melted at 287°. The 

 copper salt gave the following figures for nitrogen and copper: 



^Ber., 37, 1809 (1904). 



