76 PROTEIN POISONS 



the water-bath, cooled, and filtered to remove any tyrosin 

 and leucin that may crystallize out. The filtrate was 

 diluted to about one and one-half liters for each 100 grams 

 of cell substance, made decidedly acid with nitric acid, 

 and 20 per cent, silver nitrate added as long as it gave a 

 precipitate. It was left overnight to settle, and the silver 

 precipitate of xanthin bases filtered out. To this filtrate 

 excess of silver nitrate and barium hydrate were added to 

 remove arginin and histidin. After their removal, silver 

 and barium were precipitated by hydrochloric and sulphuric 

 acids, these inorganic precipitates boiled out with water 

 several times, the filtrate and wash water united, and con- 

 centrated. The solution, which should contain some 5 

 per cent, of acid, was treated with a 50 per cent, solution 

 of phosphotungstic acid as long as it gave an immediate 

 precipitate. The precipitate was rubbed up with 5 per 

 cent, sulphuric acid, carefully washed with the same 

 solution, and filtered with suction. The heavy white 

 precipitate was again rubbed up with water, hot saturated 

 solutions of barium hydrate added, until the mixture was 

 no longer acid, settled overnight, and the supernatant 

 liquid siphoned off. The precipitate, consisting of barium 

 phosphate, tungstate, etc., was washed several times with 

 hot barium hydrate solution, decanted, and finally filtered 

 by suction. The filtrate and wash water were united, and 

 barium was removed as carefully as possible, first by running 

 in carbon dioxide, and then by adding ammonium carbonate 

 to the solution. This precipitate, like all the other inorganic 

 ones, was boiled out several times with water, and the 

 washings added to the original filtrate. The resulting 

 liquid was concentrated nearly to dryness on the water- 

 bath, the residue taken up with water, filtered to remove 

 barium carbonate, and again concentrated to a thick 

 syrup. 



"The alkaline syrup was vigorously stirred with alcohol, 

 and then with an alcoholic solution of picric acid. Some- 

 times a crystalline precipitate came down at once, sometimes 

 there was a viscous mass like molasses candy, which became 



