On the Chemical Properties of Soils.- 31 



In conclusion, the more prominent and practically interesting 

 points which have been developed in the preceding pages may 

 be briefly stated in the following 



SUMMARY. 



1. All the soils experimented upon have the power of absorb- 

 ing ammonia from its solution in water. 



2. The sandy soil absorbed as much ammonia as the clay 

 soil. 



3. The pasture land, and probably many other soils rich in 

 organic matter, retain less ammonia than soils in which organic 

 matter does not occur in excess. 



4. The differences between sandy, calcareous, and clay soils, 

 in their power of absorbing ammonia, is not so great as is gene- 

 rally believed. 



5. Ammonia is never completely removed from its solution, 

 however weak it may be. On passing a solution of ammonia, 

 whether weak or strong, through any kind of soil, a certain 

 quantity of ammonia invariably passes through. No soil has the 

 power of fixing completely the ammonia with which it is brought 

 into contact. 



6. In the preceding experiments all the soils absorbed more 

 ammonia from the stronger than from the weaker solution ; that 

 is to say, the absolute quantity of ammonia which is absorbed 

 by a soil is larger when a stronger solution of ammonia is passed 

 through it. But, relatively, weaker solutions are more thoroughly 

 exhausted than stronger ones. 



7. Soils containing much organic matter (humic acids) at first 

 absorb less ammonia from weak solutions than others poor in 

 vegetable matter. But subsequently they take up more ammonia 

 if it is presented to them in stronger solutions. 



8. A soil which has absorbed as much ammonia as it will 

 from a weak solution, takes up a fresh quantity of ammonia when 

 it is brought into contact with a stronger ammoniacal solution. 



9. All the soils not only absorbed free ammonia, but likewise 

 removed a certain quantity from solutions of ammoniacal salts. 



10. In passing sulphate of ammonia or sal-ammoniac through 

 a soil, the ammonia alone is absorbed, and the acids pass through 

 in combination with lime or other mineral matters. 



11. A larger proportion of mineral matter is dissolved in a 

 soil when dilute solutions of ammoniacal salts are filtered through 

 it than is the case with pure water. 



12. Soils absorb more ammonia from stronger than weaker 

 solutions of sulphate of ammonia and chloride of ammonium. 



13. Not only the strength, but likewise the quantity of the 

 ammoniacal solution which is brought into contact with a soil, 



E 



