43 2 Histon and its Preparation [April 



were the sanie in this respect. Furthermore the precipitate obtained 

 with sodium chlorid was always readily soluble in 0.8 per cent. 

 hydrochloric acid Solution. 



The above mentioned results suggested different constitutions 

 for histons precipitated by sodium chlorid and by ammonia. To 

 detemiine this point pure preparations of each kind were made and 

 analysed. 



B. Methods of preparation and purification. Histon 

 hydrochlorid was obtained by the Kossel-Kutscher (16) method. 

 A portion of the clear bluish filtrate containing it was saturated 

 with sodium chlorid and filtered, and the resulting precipitate washed 

 with alcohol, dissolved in water and the Solution dialyzed in a parch- 

 ment bag for several days against running water. At the end of 

 that time the bag was transferred to a tall jar of distilled water and 

 the latter renewed daily until no trace of chlorin could be detected 

 in the histon Solution with silver nitrate. The Solution was then 

 removed from the bag, filtered and evaporated in thin layers to 

 dryness at 45° C. Light yellow flakes were obtained. (During the 

 dialysis and evaporation toluene was used as a preservative. ) The 

 flakes were ground to a white powder and dried to constant weight 

 — first in vacuo over sulfuric acid and finally at 105° C. A second 

 portion of the histon-hydrochlorid Solution was treated with am- 

 monia and the resulting precipitate washed free from all traces of 

 ammonia with water. It was then washed with alcohol and ether, 

 and dried to constant weight at 105° C. A third histon product 

 was obtained by adding a few drops of ammonium hydroxid Solu- 

 tion to a portion of the chlorin-free Solution of the sodium chlorid- 

 precipitate. The precipitate thus obtained was insoluble in water. 

 It was washed with water, alcohol and ether, and dried to constant 

 weight at 105° C. These three preparations^ were used in the 

 quantitative studies. 



In the tabulation on page 434 these preparations are designated 

 as follows: (a) sodium chlorid-precipitated histon, free from chlo- 

 rid admixture; (b) sodium chlorid-precipitated histon, reprecipi- 

 tated with ammonia; (c) ammonia-precipitated histon. 



*Inability to find a solvent for ammonia-precipitated histon which would 

 not hydrolyze it made it impossible to attempt the preparation of a sodium 

 chlorid-saturation precipitate of the ammonia-histon. 



