18 On the Chemical Properties of Soils. 



Therefore '176 grains were removed from every 1000 grains of 

 liquid of 3 '331 grains from the entire quantity of liquid used in 

 the experiment and absorbed by 3500 grains of soil. 



Ammonia. 

 Grains. 



1000 grains of this soil thus absorbed in the 2nd Experiment '9457 

 After having taken up in the 1st Experiment .. .. '576 



Or in both experiments 1000 grains of soil absorbed .. 1-5217 

 Thus in each case the soils absorbed a considerable quantity of 

 ammonia from the stronger solution with which they were brought 

 into contact after having taken up a certain variable quantity 

 from a weaker solution. 



It is singular that whilst the proportion of ammonia removed 

 by each of these five soils varied considerably in the first series 

 of experiments with the weaker ammonia solution, the total 

 quantity of ammonia absorbed by 1000 grains of soil in both 

 experiments is almost identical in four of the soils, and but little 

 less in the remaining one. Thus the total amount of ammonia 

 absorbed by 1000 grains of soil was in the case of the 



Ammonia. 

 Grains. 



1. Calcareous soil T5193 



2. Fertile loamy soil 1-5363 



3. Claysoil .. .. 1-1240 



4. Sterile sandy soil 1-5220 



5. Pasture land ' 1-5217 



It will be seen that the soil from a permanent pasture absorbed 

 much more ammonia in the 2nd Experiment than in the first, 

 so that the total quantity of ammonia absorbed in the two 

 together is nearly identical with that absorbed by the other soils. 



I have shown that this soil contained much organic matter 

 (humic acids), and that a portion of this organic matter united 

 with ammonia passed into solution in the 1st Experiment, impart- 

 ing to it a deep yellow colour. In the 2nd Experiment with a 

 stronger ammonia solution the liquid was but little coloured. 

 It appears thus that, comparatively speaking, little ammonia 

 was fixed in the soil in the 1st Experiment, because the organic 

 acids in this soil uniting with the ammonia of the weaker solu- 

 tion, produced soluble combination before insoluble compounds 

 of ammonia could be formed in the soil in as large a proportion 

 as in the other soils containing much less organic matter. 



The organic acids of the pasture soil were apparently removed 

 in the 1st Experiment, and thereby the soil acquired increased 

 powers of absorbing ammonia from the stronger solution used in 

 the 2nd Experiment. 



THIRD SERIES OF EXPERIMENTS. 



Although the preceding experiments show distinctly that soils, 

 no matter of what character, absorb more ammonia from strong 



