PEODUCTION OF SODIUM CARBONATE 303 



soil to the growth of the plant itself ; whenever a plant is fed 

 with nitrate of soda some of the base will be left behind in the 

 soil in the form of carbonate of soda. 



Collateral evidence is also forthcoming that nitrate of soda 

 gives rise to a free base in the soil evidence derived from the 

 determinations of carbonate of lime in the Rothamsted soils, 

 to which allusion has already been made. On looking back to 

 Table XCVIL, it will be seen that the plots receiving nitrate 

 of soda have been losing their carbonate of lime less rapidly 

 than the unmanured plots, 100-200 Ib. per acre per annum 

 less, though too much reliance cannot be placed on the 

 weights calculated. This reduction in the amount of carbonate 

 of lime annually removed from the soil is due to the fact that 

 the carbonate of soda formed from the nitrate of soda has done 

 part of the work for which carbonate of lime is usually 

 required, and has thus indirectly afforded it some protection 

 from waste. Both substances act alike in serving as bases for 

 such processes as nitrification. 



Though the selective action of the plant upon the nitrate 

 of soda is the main agency in producing carbonate of soda in 

 the soil, a similar action is brought about by bacteria, particu- 

 larly when the nitrate of soda is present in a water-logged soil 

 lacking aeration. Though no wholesale destruction of nitrates 

 usually occurs under field conditions, even when they are 

 applied in conjunction with an excess of farmyard manure, 

 some losses of the soil do undoubtedly occur, as may be seen 

 from the fact that in most experiments the whole of the 

 nitrogen applied as nitrate is not recovered in the crop even 

 though there has been no washing out of nitrates by drainage. 

 The bearing of denitrification upon our problem comes from 

 the fact that when the nitrogen of the nitrate of soda is thus 

 lost the soda base is left behind as carbonate of soda, hencfe 

 from some of the nitrate of soda that is not taken up by the 

 crop there will be carbonate of soda produced by the organisms 

 of denitrification. Moreover, there are other bacteria in the 

 soil which will take the nitrogen from nitrate of soda; they 



