THE USE OF MANURES. 65 



144. Peruvian guano contains less moisture than 

 African and Patagonian because the climate of Peru 

 is drier. It also has a less pungent smell of ammonia. 

 As guano is often adulterated with sand, earth, etc., 

 the following physical properties and tests will en- 

 able one who is not a chemist to distinguish between 

 a good guano and one of inferior quality, or one 

 which has been adulterated. 



145. Genuine guano is a substance of a yellow- 

 ish-brown color, of a peculiar urinous odor, and 

 has mixed with it, white lumps or fragments. When 

 heated on a shovel or iron plate, at least half of it 

 will volatilize, and nearly the whole of the remain- 

 der will dissolve in dilute hydrochloric acid. Sand 

 and earthy adulterations will be left undissolved, which 

 in good guano does not amount to more than from 

 i to 2 per cent. When first heated, it gives off 

 white vapors with a strong smell of ammonia. This 

 odor is greatly increased by the addition of lime. 

 The ash should be white or grayish ; a yellow or 

 red ash indicates an admixture of clay or earthy 

 matter. 



146. The highly stimulating effect of guano is due 

 to the large amount of nitrogenous matter which 

 it contains. The atmosphere furnishes nitrogen to 

 plants in the form of ammonia, but not in sufficient 

 quantity to meet the demands of a luxuriant growth 

 of wheat, corn, or other crop. This must be sup- 

 plied by decaying nitrogenous matter, salts of am- 

 monia, or nitrates. 



