196 GUANO. 



cannot evade the detection of the most unpractised 

 sense of smell. 



In order to be able to apply this test at any mo- 

 ment, it is judicious to keep a portion of slaked lime 

 constantly on hand. But that this may not lose its 

 effect, it must be carefully excluded from the air, and 

 should, therefore, be preserved in dry and well- 

 stopped bottles. 



4. Treatment with Hot Water. Half an ounce of 

 the air-dried guano is placed in a filter made of blot- 

 ting-paper, folded together into the shape of a cone, 

 and this put into a funnel or wire filter, and scalding 

 water poured over it until the water runs without 

 color. If the paper with the moist guano is laid, 

 when no more liquid drops from it, in a A^arm place, 

 and the residue weighed when it has become com- 

 pletely dry, the deficiency from its original weight 

 will show the weight of those elements which have 

 been dissolved by the water. As a general rule it 

 may be held, the larger the quantity of a guano that 

 is dissolved in water, the more ammoniacal salts does 

 it contain, and the better it is. Hence that guano 

 must be preferred, as in the test by combustion, 

 which, upon being so treated with water, leaves be- 

 hind the smallest residue. In the best or Peruvian 

 guanos the residue from half an ounce that is insolu- 

 ble in water amounts to about 2 drachms (from 

 50 to 56 per cent.) ; on the other hand, in the com- 

 paratively worthless guanos from 3 to 3 J drachms 

 (80 to 90 per cent). 



