316 Rain Falling at Rothanisted 



Nitrites in rainwater. 



The amount of nitrite in the Rothamsted rain has not been separately 

 estimated : it is included in the nitrate figure. The rain from the Hebrides 

 was frequently tested during the winter of 1911-12 and more frequently 

 gave negative than positive results. Rain collected on land, however, 

 usually contains nitrites and a long series of determinations made before 

 the War at Prince Troubctzkoy's Experiment Station at Ploty in 

 South Russia showed a considerable excess of nitrites in winter compared 

 with summer rains. 



The total nitrogen, in rainwater. 



No further determinations of organic nitrogen have been made 

 beyond those recorded in Dr Miller's paper. The figure there given is 

 1-35 lb. per acre per annum; assuming this to be still correct on an 

 average of the whole period the rain contained 



2-64 lb. ammoniacal nitrogen, 

 1-33 ,, nitric nitrogen, 

 1-35 ,, organic nitrogen. 



The ratios are almost exactly 



2 parts ammoniacal nitrogen, 

 1 part nitric nitrogen, 

 1 part organic nitrogen. 



But, as already pointed out, the proportions between ammoniacal 

 and nitric nitrogen have fallen recently. 



The sources of the combined nitrogen in rain. 



Sotirces of ammonia. Certain indications as to the source of the 

 ammoniacal nitric nitrogen in the air are afforded by their close relation- 

 ship with the amount of rain: when the rainfall is high the ammonia 

 is high, and conversely when the rainfall is low the ammonia is low 

 also. There appear to be two possible sources: the ammonia may be 

 brought into the district with the rain, or it may be already present in 

 the atmosphere and dissolved out by the rain : in the latter case a constant 

 renewal of the atmospheric supply has to be assumed, otherwise the first 

 rain would wash out all that was present, leaving nothing to be removed 

 later. 



If the ammonia came with the rain the whole phenomena would be 

 readily explicable: the more the rain the greater the amount of ammonia. 



