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



The results set forth in tables I, II, and III leave no room 

 for doubt as to the effects of "alkali" salts on the nitrate deter- 

 mination by the colorimetric method. Both NaCl and Na.SO^ 

 induce large losses of nitrate, and especially is this true of NaCl, 

 which may be responsible for losses equivalent to forty-five per 

 cent and more of the total nitrate present as indicated in Table 

 I. While NaoS04 induces smaller absolute losses than NaCl, they 

 are none the less marked, and where large amounts of the sulfate 

 are present very considerable losses of nitrate occur. 



Perhaps the most striking feature of the foregoing results is 

 what appeals to one at first sight as the singular difference in 

 the behavior of Na^.SO^ and NajCO,. Whereas the former is 

 always responsible for losses in the determination of nitrates, 

 the latter is the only one of the salts tested which has no effect 

 and the presence of which in a long series of tests has never, 

 except in one case, decreased the amount of nitrate present as 

 shown by the colorimeter readings. It was naturally assumed 

 that NaoCO;,, after the addition of the phenoldisulphonic acid, 

 would be converted in the presence of an excess of sulphuric 

 acid into Na.SO^ and should therefore show the same decreases 

 in the nitrate content as the latter salt. To clear up these rather 

 puzzling facts, as above given, we decided to run a special series 

 of experiments based on a suspicion which we had as to the 



