THE SOUTHERN PLANTER. 



661 



I860.] 



in definite proportions. Experiments re- 

 peated with muriate of ammonia were still 

 less so, for the absorptive power of the same 

 earth, under the same conditions, presented 

 a great regularity; but so soon as the 

 strength of the solution varied it was no 

 longer the same. 



The quartzose sandy oil, rich in organic 

 matters, but almost devoid of alumina, was 

 found to possess a considerable power in 

 fixing ammonia from its solution in water. 

 This fact seemed to indicate that in this in- 

 stance the organic matter or humus was the 

 active agent. Some vegetable mould, taken 

 from the hollow in an oak tree, was there- 

 fore subjected to experiment, when it was 

 found to fix free ammonia from its solution 

 in water. The mould, as well as peat, acted 

 towards ammonia in exactly the same man- 

 ner as arable land. These substances, in 

 short, seem to have an action on ammonia 

 identical to that of animal charcoal. They 

 all possess, for the ammonia in solution in 

 the water, an absorbent power in general 

 superior to that of arable land ; and Brust- 

 lein has the merit of making the discovery 

 that these substances are perfectly inert to- 

 wards ammonia ivhen it exists in solution as 

 a salt. . This distinction, it appears to us, 

 clears up the whole matter, in showing the 

 grounds of the fallacious inferences of Lie- 

 big and Way. The inaction of such sub- 

 stances as peat and vegetable mould for 

 salts of ammonia, is therefore no doubt at- 

 tributable to the want of alkaline or earthy 

 carbonates to decompose them, and set the 

 ammonia free and permit absorption. 



But Brustlein further subjected his hy- 

 pothesis to a still more decisive test. A 

 quantity of the calcareous earth from Be- 

 chelbronn was repeatedly washed with di- 

 luted muriatic acid, and freed from the car- 

 bonate of lime which it contained. The 

 soil thus prepared preserved intact the pro- 

 perty of absorbing ammonia in a free state 

 from solution ; but entirely lost its property 

 for absorbing salts of ammonia,. This inac- 

 tion, he inferred, could not proceed from the 

 destruction of any aluminous compound 

 analogous to those of the silicates to which 

 Professor Way assigned the special function 

 of decomposing alkaline salts. This was 

 rendered quite evident; for, on again mix- 

 ing a portion of lime, in a minute state of 

 division, with the soil which had been wash- 

 ed with hydrochloric acid, its absorbent 

 powers for the salts of ammonia were re- 



stored. It is thus beyond doubt that the 

 decomposition of an ammoniacal salt is in- 

 duced by the presence of carbonate of lime 

 or magnesia in a minute state of division, 

 and that the absorption of ammonia by the 

 soil belongs essentially to the physical con- 

 stitution of arable land. 



Brustlein further infers from his experi- 

 ments that the ammonia absorbed by the 

 soil is chiefly retained as such, being neither 

 modified nor transformed into any nitroge- 

 nous compound. In the case of humus and 

 peat, however, a portion of the ammonia is 

 destroyed by an absorption of oxygen taking 

 place, otherwise it appears to be retained by 

 the soil somewhat in the same manner as 

 the soil retains water, with this difference, 

 that water is essential to this attraction tak- 

 ing place, or within certain limits it increases 

 the power. A soil absorbs smaller quanti- 

 ties when it is dry than when it is moist. 

 Air can be almost entirely deprived of its 

 ammonia when made to traverse a long tube 

 containing moist earth : but if in this case 

 the air yields up its ammonia readily, it also 

 carries the ammonia away with great facility 

 when dried and passed over the moist soil. 

 It is found, besides, that the ammonia which 

 is fixed on filtering its solutions through a 

 soil, does not possess a greater stability than 

 when absorbed in the gaseous form. Moist 

 earth exposed to evaporation loses, along 

 with its water, a considerable quantity of 

 the ammonia absorbed. A portion of the 

 calcareous soil from Bechelbronn lost, upon 

 drying in a room where the temperature was 

 not higher at the end of the experiment 

 than- 12 degrees centigrade, more than half 

 the ammonia which it had absorbed. After 

 being watered and dried four times, it only 

 retained about one-fourth of the quantity of 

 ammonia. Nothing, therefore, it appears to 

 us, can be more completely demonstrated 

 than that the absorbing powers of soils are 

 due to their physical properties. Brustlein 

 assumes, though he has not tested the hy- 

 pothesis by experiments, that potash and 

 other bases are also retained by the same in- 

 fluences as fix ammonia. 



The fact of the absorbing powers of the 

 soil for ammonia being weaker in dilute solu- 

 tions, has naturally led Brustlein to believe 

 that a certain amount of ammonia can exist 

 in solution and circulate within the soil. 

 With Way, he imagines that the degree of 

 solubility, though small, may yet be sufficient 

 for the wants of plants, on the supposition 



