ADVANCED PHYSIOLOGICAL CHEMISTRY 427 



Histidin as a mercury salt. The precipitate (1) is collected on a filter paper, 

 suspended in water and treated with H 2 S gas to separate the Hg (as HgS) 

 which is filtered off. The mercury-free filtrate is evaporated to small bulk 

 at a low temperature, and allowed to stand, when histidin chloride crystallises 

 out. 



The filtrate (1) is rendered free of Hg as above described and treated in warm 

 solution with powdered silver sulphate. This latter is added in small portions 

 at a time until a sample of the solution, when placed in a watch glass, gives 

 a brown precipitate with baryta-water (and not, as at first, a white precipitate). 

 This test shows when an excess of silver comes to be present in the solution. 

 The silver sulphate also removes all traces of HC1 from the solution. By now 

 adding baryta-water, the excess of silver combines with Arginin to form a 

 precipitate (2) which is collected on a filter paper, washed with, and then 

 suspended in, water and the silver removed by means of H 2 S. The silver-free 

 filtrate, after being carefully neutralised with nitric acid, is evaporated to a 

 syrup, which on standing yields crystals of Arginin nitrate. 



The filtrate. (2) contains Lysin. After removing silver and barium (by 

 H 2 S and H a S0 4 ) and evaporating the filtrate from these to small bulk an 

 alcoholic solution of picric acid is added. This precipitates lysin as a picrate, 

 which is then shaken in a separating funnel with dilute HC1 and ether. The 

 HC1 displaces the picric acid from its combination, and chloride of lysin is 

 produced, which goes into solution in the ether. The latter is separated, and 

 on evaporation yields lysin chloride. 



To obtain large yields of the hexone bases it is desirable not to 

 prolong the heating of the proteid with HC1 for more than 7-8 

 hours. For glutaminic acid 3 days are necessary. 



The above method is only qualitative. A quantitative method 

 has been worked out by Kossel and Kutscher, 1 but is too compli- 

 cated for description here. 



Various attempts have been made to build up artificial proteids from 

 their decomposition products, but these attempts have not as yet been 

 successful. A substance very like proteid has, however, been pre- 

 pared by Grimaux, who by heating together certain amido bodies with 

 an aromatic radicle obtained a substance which he called Colloid, and 

 which gave most of the ordinary tests for proteids. It also caused 

 intravascular clotting of the blood when injected into the circulation 

 of an animal, thus resembling nucleo-proteids. Proteids have also 

 the power of combining with the Halogen elements to form definite 

 compounds. 



The Physical Properties of Proteids. Method of obtaining Crystals. 

 The whites of several eggs are mixed with an exactly equal amount 

 of a fully saturated solution of ammonium sulphate. This precipitates 

 the globulins. The ammonium sulphate solution must be exactly 

 neutral in reaction, and should be added to the egg-white in small 

 l Zeitschr.f. phys.Chem., Bd. .38, S. 165. 



