FORMATION OF ALKALINE CARBONATES 301 



suggested an explanation facts to which the late Mr Waring- 

 ton had drawn particular attention in a paper contributed to 

 the Journal of the Royal Agricultural College at Cirencester 

 in 1899. Warington had pointed out that when the com- 

 position of any plant is examined, the acids and bases do not 

 balance one another, but the acids are in excess. Taking the 

 ash of a plant and summing the acids phosphoric and 

 sulphuric acid, chlorine against the bases potash, soda, lime, 

 magnesia, iron there is generally an excess of bases ; but this 

 excess is turned into a deficit as soon as we bring into account 

 the nitrogen in the plant, which being burnt off is not found in 

 the ash. Yet in this connection it must be counted as an acid 

 because it entered the plant as nitrate of lime or soda one of 

 the neutral salts originally present in the soil, which pass into 

 solution in the soil water and then diffuse through into the 

 plant's roots. If then the nitrogen is calculated as nitric acid 

 and added to the acids in the plant, it is evident that the 

 ordinary crop must have taken from the soil a greater amount 

 of the acids than of the bases contained in the salts presented 

 to it as food. Table CI. shows this relation for four different 

 crops at Rothamsted, the figures given for acids and bases 

 being equivalents, i.e., reductions to a common measure in 

 which one of any acid will combine with one of any alkali, 

 while in the last two lines the excess of base left in the soil is 

 recalculated as Ib. per acre of carbonate of soda and carbonate 

 of lime respectively (see Hall and Miller, Proc. Roy. Soc., B. 77 

 (1905), 1). 



From these results it is apparent that if the plant contains- 

 such an excess of acid it must leave behind in the soil a corre- 

 sponding excess of base, because the food salts in the soil are 

 in the main neutral compounds. At this rate the plant ought 

 to make a medium in which it is growing progressively more 

 basic, or alkaline if the bases set free happen to be soluble ; 

 and some of the earlier observers like Knop and Stohmann 

 show that a culture solution containing growing plants will 

 become alkaline in course of time if the solution is not 



