[ 533 1 



any crop or not. One inch of rain-water passing out in drain 

 and containing only 10 parts of N in i million parts of water 

 would take away 2\ Ibs. of N per acre valued at is. d. in 

 England (/. e. 8d. per lb.). 



854, Plants contain N chiefly in the form of albuminoids. 

 These have very complex composition, consisting of C, H, O, 

 N and minute proportions of S and P. Vegetable and animal 

 albuminoids resemble each other closely in composition. Ordi- 

 narily albuminoids are formed in plants and they undergo very 

 little change in animals consuming these plants. 14*7 to 

 to i8'4 per cent, of the constituents of albuminoids are N, 

 and the average is taken to be 16 per cent. In estimating the 

 proportion of albuminoids in a plant, the estimated N is 

 multiplied by 6-25 (16x6-25 = 100). Some albuminoids 

 are soluble and some insoluble. In determining, however, 

 the albuminoids in vegetable substances, it is not sufficient 

 to estimate the total N, as other nitrogenous substances, 

 such as asperegin, occur in plants. The carbolic acid 

 process of determination of albuminoids is the best. Warm 

 the substance with a solution of Phenol and metaphos- 

 phoric acid which coagulates albumins and renders them 

 insoluble. Wash the precipitate with water containing 

 phenol. Then estimate the N in the precipitate in the usual 

 way. This gives the N in the albuminoids. , The N thus 

 estimated multiplied by 6*25 gives the true albuminoids. 

 Turnips contain \ to i per cent, of albuminoids ; potatoes 

 i to 2 per cent. ; cereals about 12 per cent. ; rice containing 

 less than 7 per cent., leguminous seeds 24 per cent. Albumi- 

 noids are the most nutritious food constituents of plants 

 and the most important manurial constituent of humus. N as 

 well as ash are relatively in larger quantities in young plants. 

 With increase in age C, H, and O are assimilated by plants 

 in larger and larger proportion and carbohydrates are there- 

 fore manufactured more towards the end of their growth and 

 nitrogenous matter more towards the commencement- 



