

213 



5. Suggestions for experiments with the acetate^ oxalate, and 

 humate of ammonia. 



The composition of these three salts has been given in the 

 first section of the preceding chapter. 



1. Acetate. The acetate of ammonia has been said to be 

 poisonous to growing plants. The same has also been stated 

 by Bouchardat of the carbonate, sulphate, muriate, &c. But 

 extended experience in this country has shown the latter to be 

 incorrect. It would be interesting, therefore it is necessary, 

 in fact, to the satisfactory clearing up of this point that expe- 

 riments should be made with the view of ascertaining the special 

 nature and the extent of the action, of the acetate, compared 

 with that of equivalent quantities of the other salts of ammonia. 



2. Oxalate. As the oxalic acid occurs abundantly in plants, 

 it is desirable that its influence upon their growth should be 

 ascertained. Though, in the first instance, this is a theoretical 

 inquiry, yet it is not without a practical bearing. 



Certain soils produce the sorrels (Rumex acetosa and aceto- 

 sella) in large quantities, and the addition of lime to such soils 

 extirpates these plants. Does oxalic acid exist in such soils? 

 will the application of a soluble oxalate favour the growth of those 

 plants in which oxalic acid is found or formed in any considerable 

 quantity ? How will the ammonia and the oxalic acid contained 

 in oxalate of ammonia modify the action of each other ? 



With the view of obtaining answers to these questions, it 

 would be desirable to institute comparative duplicate experi- 

 ments with the carbonate of ammonia, with oxalic acid, and 

 with oxalate of ammonia. For though, where there is lime in 

 the soil, the oxalic acid would probably unite with it to form 

 the insoluble oxalate of lime, before it had an opportunity of 

 entering into the roots of plants, still it may not be incapable, 

 even in that state of combination, of modifying the plant's 

 growth, and of throwing light upon the nature of its chemical 

 influence upon vegetation. 



3. The humate. It is a disputed point at present among 

 chemical physiologists how far the dark-coloured acid substances 

 (the humic and ulmic acids) contained in the soil contribute 



