CHAPTER VI. 

 SOURCES OF FERTILIZING MATERIALS. 



SOURCES OF NITROGEN. 



Nitrogen, as we have seen, is a gaseous substance which makes up for- 

 fifths of the atmosphere, mingling with and diluting the oxygen so that it can 

 be breathed, but never combining with it under ordinary conditions. It is 

 the oxygen of the air upon which animals depend for respiration, but it must 

 be diluted for this purpose, and hence the nitrogen is mixed with it, though 

 nitrogen takes no part itself in respiration. Plants even, which need nitrogen 

 as food, will die if confined in nitrogen gas alone. Ammonia is a hydrate 

 of nitrogen which acts as a base in connection with acids. Thus with sul- 

 phuric acid it forms the sulphate of ammonia, with carbonic acid, the car- 

 bonate of ammonia, which is the ammonia we smell so strongly escaping from 

 a heating manure pile exposed to the weather. Manufacturers of fertilizers 

 always like to print the percentage of ammonia on their bags rather than that 

 of the actual nitrogen, as the figures look larger. When you find the per- 

 centage of ammonia thus on a bag you can get the true amount of nitrogen by 

 multiplying the ammonia per cent, by 0.8235. Thus if the bag has 2 per 

 cent, ammonia printed on it, this means that there is but 1.647 per cent of 

 actual nitrogen. 



The source from which the nitrogen comes is a very important matter to 

 the purchaser of the fertilizer, since chemical analysis may show that there is 

 a large percentage of nitrogen present, but at the same time it may be almost 

 entirely useless because in an unavailable form, and all that chemical analysis 

 can tell you is that it is there. Hence it is important to know from what 



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