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



It would seem from these results therefore that lime can 

 3'ield a clear, colorless solution without decreasing the quantity 

 of nitrates present in the solution appreciably, and that it is 

 therefore the only one of the coagulating agents above tested 

 which can be safely used in the work. We commend it to soil 

 chemists and others making nitrogen determination under similar 

 conditions. Only where very large quantities of lime are em- 

 ployed, and they are not necessary, have we found definite losses 

 of nitrates. We find that 2 grams of CaO is sufficient to 

 coagulate the clay in 100 grams of loam soil and to remove 

 whatever color may be present at the same time. 



While lime has been used by some chemists in accordance 

 with the method above outlined, its use has by no means been 

 general and no data prior to this existed with reference to its 

 effects on the nitrate determination. J. G. Lipman and P. E. 

 Brown give directions in their laboratory manual on Soil Bac- 

 teriology for the use of 2 grams of lime to precipitate the clay 

 in the 100 gram samples of soil used in nitrification experiments, 

 but we have never seen any published statements beyond that 

 as to the advisability or feasibility of employing lime. It is cer- 

 tainly surprising that those who have tested the method for 

 nitrate determination should not have tried and urged the use 

 of lime as a substitute for alum or aluminum cream. 



Other Experiments on Salt Effects 



It appeared interesting, when the results in Tables I, II, and 

 III were obtained, to ascertain if the kation as well as the anion 

 of salts was responsible for losses of nitrates. Accordingly a 

 series of experiments was instituted in which the effects of 

 NaCl, KCl, and MgCU could be compared. The following re- 

 sults were obtained. 



