136 Analysis and Valuation of Manures [218-220 



ANALYSIS OF GUANO 



2 18. The name \ guano ' is applied to such a large assortment 

 of manures that no one method can be described applicable to 

 all. Any manure, therefore, bearing the simple name ' guano ' 

 should be tested with blue litmus paper. If it give a decidedly 

 acid reaction, it must be analysed by the method given for 

 superphosphates. If not, it should be proceeded with in 

 much the same manner as bones, except that the organic 

 matter must be burned off before the lime and phosphoric acid 

 are estimated. 



219. Moisture. — When a Peruvian guano is heated to 

 ioo° C, it gives off not only moisture, but also a certain amount 

 of ammonia. For ordinary commercial purposes this makes very 

 little difference, and the estimation may be performed in the 

 usual way. A more exact method is as follows : About 5 grams 

 are weighed out in a U tube. One end of this tube is connected 

 with a small wash bottle, containing 20 c.c. of seminormal 

 acid, in such a manner that when a current of air is aspirated 

 through the apparatus it passes first through the U tube and 

 then bubbles through the acid. The lower part of the U tube 

 which contains the guano is immersed in boiling water, and 

 the free tube of the wash bottle connected with an air-pump or 

 aspirator. In this manner all the ammonia which is liberated 

 is absorbed by the acid. When the U tube no longer loses 

 weight the acid is titrated with quinquinormal potash, and 

 from this the NH 3 which has been absorbed may be calcu- 

 lated. The loss of weight sustained by the guano is moisture 

 plus ammonia. The moisture may thus be calculated by 

 difference. 



220. Sand, Lime, and Phosphoric Acid.— Weigh 

 out about 2 grams of guano in a platinum dish and burn over 



