256 PHYSIOLOGY OF NUTRITION. 



After three, five, or seven days we select seedlings which are very 

 similar. They are cleansed, pounded in a mortar, and then dried, 

 at first on the water-bath with frequent stirring, and afterwards in 

 the drying chamber at a temperature of 50 C to 60 C. The resi- 

 due is now left in the air for twenty- four hours, loosely covered ; it 

 is weighed, and then samples are at once taken for determinations 

 of the quantity of dry substance. We now know the dry weight of 

 the seedlings obtained. The dry weight of the corresponding num- 

 ber of seeds is likewise known, and we are therefore in a position 

 to reduce the results of the researches folio wing to quantities of dry 

 substance corresponding with seeds and seedlings respectively. 



To determine the total Nitrogen, 1-2 gr. of dry substance of the 

 seeds and seedlings, well powdered, is examined by Kjeldahl's 

 method. (See in Konig's Untersucliung landwirthschl. wiclitiger 

 Stoffe, 1891, p. 150.) 



The Nitrogen of the proteids is determined by Stutzer's method. 

 (See Koriig, p. 212.) 



Subtracting the Nitrogen of the proteids from the total 

 quantity of Nitrogen, we obtain a result giving the quantity of 

 Nitrogen in the non-proteid compounds. The seeds contain only 

 very small quantities of such substances, while the seedlings, 

 especially fairly advanced ones, are rich in amido-acids and acid 

 amides, etc. 



To determine specially the quantity of acid amides in the re- 

 search material (in lupin seedlings asparagin is almost the only 

 substance present belonging to this group), about 8 gr. of dry 

 substance are twice extracted for an hour with 40 c.c. of cold 

 water. After filtering with the help of a suction pump, the 

 residue is boiled once with 50 c.c. of water, and then the filtrates, 

 and the fluid used for washing the residue, are put together.* 

 We now rapidly boil the fluid to precipitate the dissolved proteids, 

 filter, and boil the filtrate down to 200 c.c. 



To 100 c.c. we add 10 c.c. of Hydrochloric acid, and boil for one 

 to one and a half hours, replacing the water lost in the process ; 

 the asparagin is thus split up into Asparagic acid and ammonia. 

 The Nitrogen of the ammonia we determine in the azotometer 

 (see 92) by means of brominated soda solution (prepared by 

 dissolving 100 gr. of caustic soda in 1250 c.c. of water, and treat- 



* Should there be any difficulty in filtering the fluid after boiling, we pass 

 into it for half an hour a rapid stream of washed Carbon dioxide. The fil- 

 tration will then proceed very rapidly. 



