102 



THE ROLE OF NITROGEN IN PLANT-METABOLISM, 111., 



seeds in 10% sodivim chloride solution, which contained 3-Oi) 

 gms. of nitrogen. 



(a) To 50 CO. of the extract, were added 10 drops of a 2% 

 solution of acetic acid, then heated to boiling in the water- 

 bath for some time. The coagulated protein was filtered ; the 

 filtrate was boiled for some time longer, and the small 

 amount of precipitate obtained was added to the first. The 

 coagulum, after washing with hot water, was Kjeldahled for 

 nitrogen. The filtrate from the coagulated protein showed 

 no biuret reaction, indicating absence of peptones. On 

 titrating with alkali till neutral to phenolphthalein, no pre- 

 cipitate was observed. 



(b) Fifty cc. of the extract were precipitated by a 5% 

 tannic acid solution, and kept cool by standing in water ; 

 after spinning in a centrifuge, and washing with diluted 

 reagent, the nitrogen was estimated. 



(c) Fifty cc. of the extract were diluted with water lo 

 250 cc, and a rapid current of carbon dioxide passed through 

 it for some time. The precipitate was separated in the centri- 

 fuge. The fluid, after further diluting with an equal volume 

 of water, was again treated with the gas, when a small pre- 

 cipitate was obtained, which was added to the first, and the 

 nitrogen estimated. The filtrate was further tested by boil- 

 ing, when a coagulum formed, which was removed, and its 

 nitrogen also estimated. 



The results are stated below : — 



Table iii. 



Seeds, 100 gms. contain 



iSalt-extrauL contains 



{(i) Coagulum by boiling 



(b) Tannic acid ppt 



(c) COo j)recipitate 



P'iltrate coagulated by heat 

 Filtrate not coagulated 



% of the total 

 N of seeds 



100- 

 67-6 

 23-6 

 30 

 18-9 

 2-9 

 45-3 



