24 University of California Publications in Agricultural Sciences [Vol. 1 



with losses of nitric acid. AYliile all the investigations above re- 

 viewed have pointed out the interference of chlorine and chlorides 

 with the nitrate determination, and while some of them have 

 also considered the losses occurring through the use of Na^COs, 

 no mention is made of the effects of the most common and widely 

 spread of the alkali salts, NaoSO^, or Glauber salt. It seems fur- 

 ther to have been taken for granted that Na^COg and NaoSO^ 

 should, for obvious reasons, have the same effects on the nitrate 

 determination by the phenoldisulphonic acid method. Our re- 

 sults do not, however, bear out this opinion. Under this head 

 were also studied the effects of the kation as well as the anion 

 of salts on the same determination. 



Varjdng quantities of the salts tested were here added to the 

 same amounts of nitrates in solution, and uniform quantities of 

 salts were also tested as to their effects on varying quantities 

 of nitrates. Everyone of the following tables gives the effects 

 of one of the salts tested in accordance with the scheme above 

 indicated and in some cases also shows how the nitrate deter- 

 mination is affected by varying the quantities of both the nitrates 

 and other salts. The residue containing the salts and the nitrates 

 was treated with 2 c.c of phenoldisulphonic acid thoroughly 

 stirred for about two or three minutes, 25 c.c. of nitrate-free dis- 

 tilled water was added, and then strong ammonia drop by drop 

 until the odor of ammonia persisted and the color was per- 

 manent. The solution was then diluted as necessary and com- 

 pared in the Sargent-Kennicott colorimeter with a standard 

 solution similarly and always freshly prepared, whose strength 

 was in every case carefully tested. The results of these experi- 

 ments are given in the following tables. 



