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



, TABLE IX 



Effects of Dry Mixing of Nitrates and Salts 



The data in Table IX make it quite clear that the losses due 

 to NaoSO^ occur only when the latter salt is present in solution 

 with nitrates and the solution is evaporated on the steam bath. 

 Wlien, however, the salt is mixed dry with the dry nitrate no 

 losses of the latter occur any more than they do when NaoCOg is 

 added. The same is not true, however, of XaCl, as is shown in 

 the last table. That salt causes losses of nitrates during both 

 the evaporation on the steam bath and the reaction setting 

 chlorine free in the treatment of the dry residue with phenoldi- 

 sulphonic acid. This latter fact is a confirmation of work done 

 by Gill and reviewed above. We have thus shown the individual 

 reaction of each of the salts as related to the nitrate determina- 

 tion and the causes which are responsible for the difference. 

 Nitric acid is evidently set free from nitrates through the com- 

 bined action of heat and the SO^ radicle on the steam bath and 

 in the evolution of chlorine when the phenoldisulphonie acid is 

 added to nitrate and chloride-containing material. Na._,C03, 

 however, possessing only a weak and unstable acid radicle is 

 powerless to set free nitric acid either through the help of heat 

 on the steam bath or by its reaction with the phenoldisulphonie 

 acid. 



Gener.vli E em arks 



So many factors may interfere with the determination of 

 nitrates by the phenoldisulphonie acid method that it would ap- 

 pear to be almost worthless, and yet it would seem to ils that 

 since there is no other good method to take its place which is 

 nearly as simple and capable of use ni very numerous deter- 

 minations, it is worth while taking certain precautions to avoid 



