I860.] 



THE SOUTHERN PLANTER. 



389 



The solubility in the same fluids of phosphate of magnesia and ammonia is still 

 greater. 



220 lbs. of 



In solution in water, in 



Dissolve of phosphate of 

 magnesia and ammonia, PO. 

 2MgO, NH4O. 



Sulphate of ammonia, 

 Common salt, 

 Nitrate of soda, 



732B galls. 

 11,000 

 7326 " 



9 lbs. 



13^ 

 lOi " 



The quantity of the earthy phosphates 

 taken up by the above fluids does not rise in 

 proportion with the amount of salts in solu- 

 tion, but rather tn the contrary with the di- 

 lution of these fluids. 



It is quite conclusive from these facts, 

 that water containing a very small quantity 

 of common salt, nitrate of soda, or a salt of 

 ammonia, acquires thereby the power, (which 

 alone it does not possess, or only in a slight 

 degree) of dissolving phosphoric acid, in the 

 form of earthy phosphates. These feeble 

 solutions, therefore, react towards earthy 

 phosphates like solutions of carbonic acid in 

 water. 220 lbs., for example, of sulphate 

 of ammonia produce the same solvent effect 

 on phosphate of lime as 1038^ galls, of car- 

 bonic acid in solution in water; and 220 

 lbs. of common salt dissolve as much phos- 

 phate of magnesia and ammonia as a watery 

 solution of 760i galls, of carbonic acid. 



Direct experiments prove, that a very 

 dilute solution of the same salts, take up 

 phosphoric acid from a soil which contains 

 earthy phosphates in excess, and that this 

 dissolved acid is again given up by this so- 

 lution to a similar soil which is not already 

 saturated with phosphoric acid. 



If we submit to a close scrutiny the com- 

 portment of the salts of ammonia, nitrate of 

 soda, and common salt towards soils, we find 

 that not one of these salts acts ii* the same 

 form in which it has been added to the 

 ground. 



The salts of ammonia are immediately de- 

 composed by the soil ; the ammonia is retain- 

 ed, whilst the acid enters into combination 

 with lime, magnesia, alkalies, or, in short, 

 with any basic substance in immediate con- 

 tact and capable of combining with it. 



The action of these salts is therefore of a 

 two-fold nature. On the one hand, they en- 

 rich the soil with ammonia ; on the other, 

 their acid gives rise to new compounds 

 which come into operation. The alkalies 

 and alkaline earths which combine with the 

 acid acquire thereby a greater degree of 

 solubility, and are more readily difi'used 



through the soil. If the ground is rich ia 

 magnesia or lime, the salts of these bases 

 are formed ; but their influence, with the 

 exception of that of gypsum, on certain 

 plants cannot be estimated very high. The 

 use of sal-ammoniac, instead of sulphate of 

 ammonia, gives rise to chloride of magne- 

 sium, and chloride of calcium, which act 

 rather unfavourably than otherwise on vege- 

 tation. That salts of these bases are gene- 

 rated by the action of soils on salts of am- 

 monia, and that the new salts exert no par- 

 ticularly favourable influence on the increase 

 of produce, are facts on which no doubt can 

 rest. 



If, however, portions of the soil contain- 

 ing in some places phosphate of lime or of 

 magnesia in the form of coarse grain, or 

 powder, or bone earth, come in contact with 

 these ammoniacal fluids, then there follows 

 solution of these earthy phosphates, and their 

 consequent diff"usion through the soil. 



Potash salts resemble those of ammonia 

 in the rapidity of their decomposition in 

 contact with soils ; but the comportment of 

 soda salts is quite difi"erent. 



On slowly filtering a solution of nitrate of 

 soda (containing one-fifth per cent, of salt) 

 through an equal volume of Bogenliausen 

 loam, half of the salt passes through unab- 

 sorbed, whilst the other half is converted 

 into nitrate of lime and nitrate of magnesia. 

 Under the same circumstances three-fourths 

 of a solution of chloride of sodium remain 

 undecomposed. 



If, therefore, a field is manured with ni- 

 trate of soda or common salt, and the soil 

 becomes saturated with a dilute solution of 

 these salts formed by rain, a great portion of 

 them will remain unchanged in the ground, 

 and must exercise on the moist soil an action 

 which, though in itself feeble, becomes pow- 

 erful by its continuance. 



Like the salts of ammonia, or a watery 

 solution of carbonic acid produced by the 

 decay of organic matter in manures, a solu- 

 tion of these salts, wherever they come in 

 contact with spots containing accumulations 



