248 



GUANO. 



upon evaporating the solution. But if the guano is 

 moistened with water, without lixiviating, and is then 

 left to itself, it is found, upon extracting with water 

 portions of the mixture from time to time, that the pro- 

 portion of the oxalic acid in the solution gradually de- 

 creases, w r hilst that of the phosphoric acid increases. A 

 decomposition takes place in this moistened condition 

 of the guano, through the agency of the sulphate of am- 

 monia, by which the phosphate of lime is converted into 

 oxalate of lime and phosphate of ammonia. Peruvian 

 guano is, in this respect, a very remarkable mixture, 

 which could scarcely have been more ingeniously com- 

 pounded for the purposes of the nutrition of plants ; for 

 the phosphoric acid in it becomes soluble only in a 

 moist soil, through which it then spreads in form of 

 phosphate of potash, phosphate of soda, and phosphate 

 of ammonia. 



The action of guano may rather be compared to a 

 mixture of superphosphate of lime, ammonia, and salts 

 of potash, which, indeed, in many cases, is equal to it. 

 On a soil abounding in lime, guano is, however, decid- 

 edly more advantageous than superphosphate of lime, 

 since the latter, upon coming in contact with the car- 

 bonate of lime in the soil, is at once converted into neu- 

 tral phosphate of lime, which requires to meet with 

 another solvent at the place of formation to effect its 

 diifusion through the soil, whilst phosphate of ammonia 

 spreads through a lime soil just as if there w T as no car- 

 bonate of lime in it. The phosphate of ammonia formed 

 when guano is moistened with water (PO 5 + 3NH 4 O), 

 loses in the air one-third of the ammonia. It is owing 

 to this circumstance that guano, when quite dry, will 

 keep without alteration ; whereas, when it has been 

 fraudulently moistened, to increase the w r eight, it loses, 

 by keeping, considerably in ammonia. 



If guano, just before its application on the field, is 

 moistened with water and a little sulphuric acid, suf- 

 ficient to give the water a slightly acid reaction, the 

 decomposition now mentioned, which otherwise requires 

 days and weeks, is effected in a few hours. 



