Guano 



to which they are added. They have in every case 

 the fault of artificial manures, that they cost too 

 much. Their use is not advised, because the farmer 

 can always find the fertilising matters they contain 

 at a more advantageous price. 



But a real and notable improvement in this 

 poorer guano was to treat it with sulphuric acid, 

 [H2SOJ, so as to fix the nitrogen, which is lost in the 

 decomposition of the carbonate of ammonia in the 

 form of sulphate of ammonia, and to transform 

 the insoluble tribasic phosphates into soluble and 

 directly assimilable superphosphate. This is done 

 on a large scale, and the results are called 

 dissolved guano. 



Compared to the original guano, this guano is of 

 equal content, but of much superior value. Its 

 action is more rapid and more energetic, but it will 

 not be felt for more than a year. The imits of 

 fertilising matter can be bought at the price of the 

 type units, but should not be dearer. 



Good modem nitrogenous guano is the fresh dung 

 of birds. Its value varies considerably, according 

 to its content of nitrogen and phosphoric acid. The 

 proportion of potash does not change much. It 

 contains from 2-5 to 11-5 per cent, nitrogen, with an 

 average of more than 4 per cent., corresponding to 

 3 to 14 per cent, of ammonia, 15 to 40 per cent, phos- 

 phate, in the tricalcic form [(CaO)3P205], 2 to 4 per 

 cent, potash. It is nearly always bought too dearly, 

 for its value is not equal to that of dissolved guano. 



Phospho-guano only contains i to 3 per cent, 

 nitrogen, but may occasionally contain 65-70 per 

 cent, tribasic phosphate. Neither in nitrogen nor in 



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