362 AGRICULTURAL ANALYSIS 



liters and keep in a flask free of carbon dioxid. A solution of 

 barium hydroxid is to be preferred to the corresponding sodium 

 compound for titration. If traces of carbonate be formed in the 

 two liquids, the sodium salt will remain in solution while the 

 barium compound will settle at the bottom of the flask. 



The Indicator. The indicator used to determine the end of 

 the reaction is made by dissolving one gram of rosolic acid in 

 50 cubic centimeters of alcohol. From one to two drops are 

 enough for each titration. The color reaction is less definite as 

 the quantity of ammonia in the liquid increases. When the titra- 

 tion solutions have been prepared as above described it is found 

 to require about 90 of the barium hydroxid to neutralize 20 cubic 

 centimeters of the sulfuric acid. 



By direct titration with sodium carbonate it is ascertained how 

 many grams of nitrogen the 20 cubic centimeters of sulfuric acid 

 represent. 



Example. Suppose the weight of the dried sodium carbonate 

 prepared as above directed is 0.6989 gram. 

 i/2Na 2 CO 3 , i/2N 2 



Then 0.6989 : 53 x : 14 



Whence x = 0.184615 gram of nitrogen. 



Suppose further that 20 cubic centimeters of sulfuric acid 

 solution require 94 cubic centimeters of barium hydroxid for com- 

 plete saturation and after treatment with the above amount of 

 sodium carbonate, 10^2 cubic centimeters of the barium solution 

 to neutralize the remaining acid. 



Then 9410.5=83.5 



And 0.184615 : 83-5=x:94. 



Whence x = 0.207830 gram of nitrogen corresponding to 20 

 cubic centimeters of the sulfuric acid used. 



Then 0.20783-^94 = 0.002211 gram of nitrogen correspond- 

 ing to one cubic centimeter of the barium hydroxid solution. 



If then in the analysis of a fertilizer it is found that 60.5 cubic 

 centimeters are required to neutralize the excess of sulfuric acid 

 after distillation, the percentage of nitrogen in the sample is found 

 as follows : 



