4 



absorbed by tbe surrounding soils. Some localities produce such great 

 quantities of nitrate of lime (wbich is a salt easily absorbing water) as 

 to convert tbe soil in tbeir immediate neighbourhood into a plastic 

 paste. In all the deposits such as are described ab >ve are found large 

 quantities of phosphoric acid and sufficient remains of animal life to 

 show in a positive manner their origin. It is thus seen that there is a 

 very marked difference between the character of the deposits of nitric 

 acid due to terrestrial animal origin and those which have been derived 

 from a marine vegatable source An economic observation of some im- 

 portance may be made here, viz. : To the effect that when in the future 

 the deposits of nitrate of soda due to marine origin are exhausted, it 

 may still be possible to keep up the supply .demanded for agricultural 

 use by leaching the highly impregnated soils above mentioned and thus 

 securing the nitric acid in a form sufficiently concentrated to make its 

 transportation profitable. 



PROPERTIES OF NITRATE OF SODA 



Practically the only form of oxidised nitrogen which is of commercial 

 importance from an agronomic point of view, is sodium nitrate, com- 

 monly known in commerce as Chile saltpetre. The nitrate of potash, a 

 nearly-related salt, is also of a high manurial value, but on account of 

 its.cost and the importance of its use in the manufacture of gunpowder, 

 it has not been very extensively applied as a fertilising material. When 

 Chile saltpetre is applied to a growing crop it becomes rapidly dissolved, 

 especially at the first fall of rain or by the moisture normally existing 

 in the soil. It carries thus to the rootlets of plants a supply of nitrogen 

 in the most highly available state. There is, perhaps, no other kind of 

 plant food which is offered to the living vegetable in a more completely 

 predigested state and none to which the growing plant will yield a 

 quicker response. By the very reason of its high availability, however, 

 it must be used with the greatest care. A too free use of such a stimu- 

 lating food may have, in the end, an injurious effect upon the crop, and 

 is quite certain to lead to a waste of a considerable portion of expensive 

 material. For this reason, Chile saltpetre should be applied with ex- 

 treme care in small quantities at a time, and only when it is needed by 

 the growing crop. It would be useless, for instance, to apply this ma- 

 terial in the autumn with the expectation of its benefiting the crop to a 

 maximum degree the following spring. If the application of the ma- 

 nure should be made just previous to a heavy rain, it is not difficult to 

 see that nearly the whole of it might be removed beyond the reach of 

 tbe absorbing organs of the plant. 



DECOMPOSITION OF SODIUM NITRATE. 



The molecule of sodium nitrate is decomposed in the pocess of ab- 

 sorption of the nitric acid. The plant presents a selective action to its 

 constituents, the nitric acid entering the plant organism and the soda 

 being rejected. Soda, however, may not be without its uses, for doubt- 

 less being at some time in a practically nascent or hydrated state, it 

 may play a role of some considerable importance in decomposing parti- 

 cles of minerals containing phospheric acid. It is probable that the 

 decomposition of the sodium nitrate takes place in the cells of the ab- 

 sorbing plant. For it is difficult to understand how it could be accom- 

 plished externally except by a denitrifying ferment. While the soda 

 itself is, therefore, of little importance as a direct plant food, it can 



