8 BULLETIN" 158, U. S. DEPARTMENT OF AGRICULTURE. 



Van Slyke has shown that certain corrections must be applied in the 

 method, owing to the fact that the phosphotungstates of the diamino 

 acids are slightly soluble, and these corrections have been applied 

 just as though the fractions contained only the hydrolysis products 

 of pure proteins. In Table V the combined results of the analyses are 

 given. 



The above analytical procedure which separates the nitrogen into 

 different groups, gives results than can only be rigidly interpreted 

 when the products of the acid hydrolysis are known. The results of 

 the analysis of base goods by this method can only be clearly under- 

 stood when further facts regarding the compounds, in which the 

 nitrogen is contained, are discovered. A description of the methods 

 used in isolating and identifying certain of these compounds follows. 



ISOLATION AND IDENTIFICATION OF DEFINITE COMPOUNDS FROM 

 THE PROCESSED FERTILLZER. 



Ten pounds of base goods were extracted by boiling for 1 hour with 

 20 gallons of water in a steam-jacketed kettle. The solution was 

 filtered from the insoluble residue, made exactly neutral with caustic 

 soda, the precipitate formed filtered off, and the nitrate concentrated 

 in a steam kettle to a volume of about 3,500 c. c. 



This solution contained phosphates, sulphates, and much other 

 mineral matter. In order to separate as much of these salts as pos- 

 sible from the organic compounds a cold saturated solution of barium 

 hydroxide was added to the solution until no further precipitation 

 took place. The heavy precipitate which formed was filtered off by 

 suction and washed many times with water. The filtrata was exactly 

 neutralized with sulphuric acid and concentrated to a volume of about 

 2,000 c. c. After cooling, this solution was made acid to 5 per cent 

 with sulphuric acid and a solution of phosphotungstic acid was added 

 to slight excess, and the mixture allowed to stand. 



After 3 days the precipitate which formed was filtered off and 

 washed with water containing about 5 per cent sulphuric acid and a 

 little phosphotungstic acid. The precipitate was carefully dissolved 

 in 45 per cent caustic-soda solution, using phenolphthalein as an indi- 

 cator and adding at no time more than two drops of the alkali solution. 

 Water was added so that a volume of about 1,500 c. c. was reached, 

 and barium hydroxide solution was added until the phosphotungstic 

 acid was precipitated. After filtering off the barium phosphotung- 

 state, the free alkali was just neutralized with sulphuric acid, and the 

 solution was then evaporated almost to dryness with barium carbonate 

 in order to ex^>el all of the ammonia. The residue was taken up in 

 about 1,000 c. c. of hot water and filtered, and the precipitate washed 

 with hot water. The filtrate was placed in a 5-liter flask and treated 

 while hot with solid silver sulphate, which was added slowly until the 



