IX] PROTEINS AND AMINO-ACIDS 151 



trated hydrochloric acid in a round bottomed flask heated on a water-bath. Then add 

 10 gms. of good blood charcoal (Merck's if possible) and boil on a sand-bath with a 

 reflux condenser for six hours. Filter, and evaporate the filtrate in vacuo to about 

 75 c.c. Put the residue into a narrow cylinder, stand this in ice and saturate with 

 dry hydrochloric acid gas. (This is prepared by slowly dropping strong sulphuric 

 acid from a separating funnel fitted into a flask containing strong hydrochloric acid, 

 and then passing the gas evolved through a second flask of strong sulphuric acid.) 

 Keep the liquid in a cool place for 24 hours, then cool with ice. Crystalline gluta- 

 minic hydrochloride will separate out. Add an equal volume of ice-cold alcohol and 

 allow the mixture to stand. Filter on a porcelain funnel through hardened filter- 

 paper or linen. Wash with ice-cold strong hydrochloric acid. Dry in a desiccator 

 over potash and sulphuric acid. Glutaminic acid can be prepared from the hydro- 

 chloride by dissolving this in the minimal amount of water and adding 5*3 c.c. of 

 normal caustic soda solution for every gram of product taken. If the solution is 

 then evaporated and cooled, glutaminic acid will separate out. 



Arginlne has been isolated from seedlings of Lupinus, Gucurhita^ 

 Vicia, and Pisum. It is especially abundant in the seedlings of some 

 Coniferae, i.e. Picea eoocelsa, Silver Fir (Abies pectinata) and Scotch Fir 

 (Pinus sylvestris). It also occurs in roots and tubers, as for instance in 

 those of the Turnip (Brassica campestris), Artichoke (Helianthus tubero- 

 sus), Chicory (Cichorium Intybus), Beet (Beta vulgaHs), Potato and 

 Dahlia, and in the inner leaves of the Cabbage (Brassica oleracea). 



Lysine has been isolated from seedlings of Lupinus, Vicia and Pisum. 

 Also from the inner leaves of the Cabbage and tubers of the Potato. 



Phenylalaline has been isolated from seedlings of Lupinus luteus, 

 Vicia sativa and Phaseolus vulgaris. 



Tyrosine is very widely distributed. It is present in seedlings of 

 Vicia sativa, Gucurbita, Lupinus, Tropaeolum and tubers of Potato, 

 Turnip, Dahlia, Beet and Celery. Also in berries of Elder (Sambucus), 

 in Clover (Trifolium), Bamboo (Bambusa) shoots and other plants. 



Proline has been isolated in very small quantities from etiolated 

 seedlings of Lupinus albus. 



Histidine has been isolated from seedlings of Lupinus and tubers of 

 Potato. 



Tryptophane is an important amino-acid and is the one most readily 

 detected on account of the characteristic pink or magenta colour given 

 in its free state with bromine water. The glyoxylic reaction (see p. 136) is 

 given by tryptophane in either the combined state in the protein molecule 

 or in the free state. It has been isolated from seedlings of Lupinus albus 

 and Vicia sativa. 



