msw^ ->& tfp 

 8 On the Chemical Properties of Soils. 



with a standard solution of sulphuric acid of known strength. 

 It being known how much of the test acid was required to 

 neutralise the ammonia solution before contact with soil, the 

 amount of ammonia retained in the soil could be readily cal- 

 culated : Ammonia. 



Grains. 



Before contact with the soil the solution contained in 



1000 grains .. ... '332 



After contact ;/ u,n-n [:m: "135 



Difference -197 



197 grains of ammonia were thus removed from each 1000 

 grains of solution, consequently 2*758 grains of ammonia were 

 removed from 14,000 grains of solution and retained in 3000 

 grains of soil. 



In this experiment accordingly 1000 grains of soil ab- 

 sorbed "9193 grains of ammonia. A repetition of the same 

 experiment gave precisely the same results. The clear liquid 

 poured off the soil being slightly yellow, it occurred to me 

 that the organic matter (humus acids) in the soil possibly 

 might have neutralised a small portion of the free ammonia 

 of the ammoniacal liquid employed in the experiment. As 

 the test-acid cannot indicate any ammonia when previously 

 neutralised by the organic acids of the soil, the proportion of 

 ammonia retained by the latter may be stated rather too high. 

 In order to verify this supposition, I distilled some of the yellow- 

 coloured liquid with caustic potash, in an apparatus which was 

 so constructed that all chance of traces of potash being carried 

 over with the distillate was entirely avoided. The distillate was 

 collected in a measured quantity of acid of known strength, and 

 the amount of ammonia distilled over, carefully determined. 



Proceeding in this manner, 1000 grains of liquid, after contact 

 with soil, contained *143 of ammonia. Before contact with soil 

 it contained '332 grains. Consequently *189 were removed 

 from every 1000 grains of liquid, or 2 '646 were removed from 

 the whole quantity of liquid employed in the experiment, and 

 retained by 3000 grains of soil, or 1000 grains of soil absorbed 

 "882 grains of ammonia. Not taking into account the amount 

 of free ammonia neutralised by the organic acids of the soil, 

 1000 grains of the latter, as we have seen, absorbed '9193 grains 

 of ammonia. The difference between *9193 grains and "882 

 grains is *0373 grains, and represents the quantity of ammonia 

 neutralised by the organic matters contained in 1000 grains of 

 the soil. This difference is very small, but it nevertheless con- 



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