EXPERIMENTAL. 75 



with an excess of copper hydroxide. The filtered solution was evaporated 

 to dryness under reduced pressure and the residue boiled with absolute 

 alcohol. The undissolved part was dissolved in water, freed from copper by 

 hydrogen sulphide, and the solution again evaporated to dryness under 

 reduced pressure. The residue was boiled with absolute alcohol, in which 

 all of it dissolved. The alcohol was evaporated off under reduced pressure, 

 the residue dissolved in 500 cc. of water and again converted into the copper 

 salt. By concentration 19.91 grams of crystalline racemic proline copper 

 salt were obtained, which is equal to 13.98 grams of a-proline. This was 

 recrystallized from water and dried in the air. 



Water : 0.7789 grain substance lost 0.0856 gram H 2 at no. 



Calculated for C 10 Hi 6 O 4 N 2 Cu 2H 2 0, H 2 11.00 p. ct. ; found, H 2 10.98 p. ct. 



Carbon and hydrogen : 0.6S51 gram substance, dried at no, gave 1.0310 gram C0 2 and 



0.3450 gram H 2 0. 

 Copper: 0.2926 gram substance gave 0.0799 gram CuO. 

 Calculated for C 10 H 16 O 4 N 2 Cu, C 41. 11, H 5.54, Cu 21.79 P- ct \ found, C 41.04, H 5.59, 



Cu 21.81 p. ct. 



The r-proline copper salt was freed from copper with hydrogen sulphide, 

 its solution evaporated to dryness, and the residue recrystallized from alcohol. 

 After drying in vacuo over sulphuric acid the r-proline melted at 203 to 

 205V 



Carbon and hydrogen: 0.3373 gm. substance gave 0.6424 gin. C0 2 and 0.2453 g m - H 2 0. 

 Calculated for C 5 H 9 2 N, C 52.12, H. 7.90 p. ct. ; found, C 51.94, H 8.08 p. ct. 



The solution of the alcohol-soluble copper salt was evaporated to dry- 

 ness and left a residue of /-proline copper salt which, dried at 120 , weighed 

 71.62 grams, which is equal to 56.51 grams of free /-a-proline. 



Copper: 0.2850 gram substance, dried at 110, gave 0.0760 gram CuO. 

 Calculated for Ci Hi 6 O 4 N 2 Cu, Cu 21.79 P- ct - ; found, Cu 21.30 p. ct. 



One-half of this proline copper salt was freed from copper, and the pro- 

 line racemized by heating with 150 cc. of water containing 80 grams of 

 crystallized barium hydroxide for 5 hours at 150 . The barium was re- 

 moved quantitatively with sulphuric acid, the solution concentrated, and the 

 proline again converted into the copper salt. There was thus obtained 20. 1 

 grams of very nearly pure racemic a-proline copper. 



Water : 0.3356 gram substance, air-dry, lost 0.0369 gram H 2 at 110 . 

 Copper : 0.2640 gram substance gave 0.0640 gram CuO. 



Calculated for C 10 H 16 O 4 N 2 Cu " 2H 2 0, H 2 11.00, Cu 19.40 p. ct. ; found, H 2 11.00, Cu 

 19.35 p. ct. 



1 Willstaeter, R., Berichte der deutschen chemischen Gesellschaft, 1900, xxxiii, p. 1160; 

 Fischer, Emil, ibid., 1901, xxxiv, p. 458. 



