36 University of California PubUcations in Agricultural Sciences [Vol. 1 



to the former in the investigations above reviewed. While higher 

 absolute results may no doubt be obtained from the use of KOH 

 than from XH^OH, and while in addition ammonia possesses 

 other objectionable features, we were not aware of the first of 

 these objections when these investigations were begun and did 

 not deem the others serious enough to warrant a change in the 

 established method. ]\Ioreover, the same relative values would 

 exist for the data above given if obtained with one or the other 

 of the hydrates, and therefore our results, having been obtained 

 throughout by the use of ammonia, do not in any way lose their 

 value. We do intend, however, in the future to emplo}^ KOH 

 exclusively in nitrate determinations made in this laboratory. 

 Finally we desire to call the attention of soil chemists to the 

 fact that losses of nitrates by the agencies above described never 

 seem to occur in accordance with anv definite law, with the 

 exception of the case in which the various alkali chlorides are 

 compared. In these it would appear, from calculations which 

 we have made, that the losses of nitrates are proportional to 

 the amounts of chlorine present. While no law can be formu- 

 lated, however, in accordance with which nitrates are lost in 

 the presence of salts, it may be possible to work out tables 

 for the losses of nitrates incurred in the presence of varying 

 quantities of chlorides and sulphates, and to make corrections, 

 therefore, in samples whose composition is unknown after alkali 

 determinations are made. It is true, however, that calculation 

 has shown on the basis of data in Table YIII that the losses 

 of nitrates induced by chlorides alone are proportional to the 

 amount of chlorine present. 



CONCLUSIONS 



1. The "alkali" salts NaCl and NaoSO^ induce losses of 

 nitrates when the latter are determined by the phenoldisulphonic 

 acid method. Na.CO^ has no such effect. NaCl induces much 

 greater losses than NaoSO^. 



2. Among the substances used to coagulate clay and organic 

 matter from solutions in which nitrates are to be determined, 

 potash alum, aluminum cream, and bone black have been found 

 decidedly unreliable. They all induce large lo.sses of nitrates. 



