NITRATE OF SODA. 207 



others it affords great benefit. We can only furnish 

 an explanation of this seeming caprice by a reference 

 to the chemical composition of the soil upon which 

 it is applied. If the advantages attending the ap- 

 plication of nitrate of soda are due to the alkaline 

 base which it contains, then it is evident that this 

 manure can be of small value on soils containing a 

 quantity of alkalies sufficient for the purposes of the 

 plants grown upon them; whilst, on the other hand, 

 such as are deficient in these must experience benefit 

 through its means.* In certain cases in which ni- 

 trate of soda has failed, nitrate of potash (common 

 saltpetre) has been very successful. Analyses of 

 w^heat grown with nitrate of soda and nitrate of pot- 

 ash would be of interest, in order to determine 

 whether a mutual substitution of their respective 

 bases is effected. It is to be hoped that future ex- 

 periments will throw more light upon the action of 

 this interesting manure, for theory cannot be satisfied 

 with those already existing. It has been usual to 

 employ a less quantity by weight of nitrate of pot- 

 ash than of nitrate of soda. This procedure seems 

 rather empirical, for unless sanctioned by experience, 

 it would a priori appear to be better to add the 

 greatest quantity of that salt which possesses the 

 highest equivalent. Now the equivalent of nitrate of 

 potash is considerably higher than that of nitrate 

 of soda. 



Charcoal in a state of powder must be considered 

 as a very powerful means of promoting the growth 

 of plants on heavy soils, and particularly on such 

 as consist of argillaceous earth, f 



* General Sir Howard Elphinstone informs me, that he found car- 

 bonate of soda (soda ash) an excellent manure for his land. The crops 

 obtained by means of it presented the same general characters as those 

 manured with nitrate of potash, and exhibited a greater intensity of 

 color. If this is found uniformly to be the case, it will very much 

 strengthen the supposition that the action of nitrate of soda is due to 

 its alkaline constituent — Ed. 



t For much valuable information on the subject of manures, see 

 "Agricultural Chemistry," Vol. VIII. of Sir H. Davy's collected 

 Works. 



