THE COMPOSITION OF THE SOIL 1 1 1 



Baumann and Gully (io3) applied this idea to the case of 

 peat and showed that it fully explained all the facts then 

 known. 



In the first instance they pointed out that it was not 

 necessary to assume that the " acid " was a decomposition 

 product because the original sphagnum was almost as "acid" 

 as the peat. 



Secondly, the acid if it exists must be insoluble because 

 the water extract of the peat is practically neutral to 

 litmus. 



It must, however, be very potent, because solutions of neutral 

 salts such as calcium chloride, sodium nitrate, etc., are decom- 

 posed with liberation of free hydrochloric and nitric acids when 

 treated with peat or sphagnum. 



Baumann and Gully argue that no acid of this character 

 is known to chemists, and it involves less strain to conceive of 

 a physical absorption of the base from the dissolved salt with 

 liberation of the acid than to imagine an insoluble organic 

 acid capable of decomposing simple salts in solution. 



Further reasons for supposing that the phenomena are due 

 to absorption and not to chemical action are : — 



1. The amounts of acid liberated from equivalent quantities 

 of different salts of the same base are not equal as they should 

 be in a chemical action. 



2. The amounts of base absorbed are not equivalent, e.g. 

 potassium is absorbed to a greater extent than sodium. 



3. The amount of action varies with the concentration of 

 the solution and the mass of the sphagnum, but not in the way 

 that would be expected of a chemical change. 



4. The electrical conductivity of peat is very low, much 

 less than that of an acid having the same solvent action on 

 tricalcic phosphate. 



The view that acidity of the mineral acid soils is due to 

 preferential absorption of the base was developed by Harris 

 (124) in an investigation of Michigan soils. The phenomena 

 are substantially the same as for peat : the soil turns blue 

 litmus red : an aqueous extract is neutral : but an extract 



