GUANO. 283 



value of the guano. It is important to test this 

 manure, since different specimens consist not only of 

 various kinds of genuine guano of different degrees 

 of richness, but samples also come into the market 

 which are adulterated with common earth, loam, 

 lime, sand, pebbles, and crude common salt or Glau- 

 ber's salt. 



Genuine guano presents the appearance of a moist 

 yellowish-brown earth, mixed here and there with 

 white fragments or lumps. Very few and rare speci- 

 mens are white. It has a peculiar excrementitious or 

 urinous odor, and a feeble penetrating saline taste. 



It is chemically tested in the following manner : 



I. The guano is mixed, in a dish, with hydrate of 

 lime (slaked lime stirred with water to a thin cream), 

 when it should emit, especially when heated, a power- 

 ful odor of ammonia. In order to compare different 

 specimens, the same quantity, say J oz. of each, is taken. 

 Since the value depends partly upon the amount of 

 ammonia present, the better sorts of guano will evolve 

 the stronger odor of that gas. 



II. Two ounces (or from 50 to 60 grins.) of guano, 

 finely powdered and uniformly mixed, are weighed in 

 a counterpoised porcelain capsule, and heated on a 

 water-bath until it is perfectly dry and suffers no far- 

 ther diminution of weight. The loss of weight expresses 

 the amount of moisture contained in the guano. Good 

 guano loses only between 8 and 15 per cent, of water, 

 but if fraudulently moistened, it may lose 20 per cent., 

 or even more. 



III. Half an ounce (or from 15 to 20 grms.) of guano 

 is weighed, and heated over a large spirit-lamp, or 

 gas-burner, in a porcelain or platinum crucible, with 

 free access of air, until all organic matter has burnt 

 off', and the guano is converted into a white or grayish 

 ash. Good guano, when treated in this way, leaves 

 from 30 to 35 per cent, of ash, while bad guano leaves 



20* 



