232 GUANO. 



of the preceding in that these contain a larger quan- 

 tity of the alkaline earths than is necessary to com- 

 bine with the phosphoric acid, so that the total 

 amount of that acid is separated upon adding am- 

 monia. The precipitate is immediately filtered off, and 

 the filtrate mixed, first with sulphide of ammonium, 

 to precipitate the manganese, then with oxalic acid for 

 the lime, and lastly with phosphate of ammonia to 

 separate the magnesia. Any excess of phosphoric 

 acid may be separated, as directed above, from the 

 alkalies, which are then weighed as chlorides or sul- 

 phates. 



The stalks of the Graminacese usually leave an 

 ash which cannot be completely decomposed by nitric 

 or hydrochloric acid. The weighed silicate remaining 

 undissolved, is decomposed most conveniently with 

 hydrofluoric acid, and the bases, previously in combi- 

 nation with silicic acid, may then be estimated in the 

 solution. The silicic acid is determined from the 

 loss. In this case, the determination of the charcoal 

 and sand must, of course, be omitted. 



(See also for other, and, in part, newer and better 

 methods, Liebig's and Kopp's Jahresbericht ; 1850, p. 

 603; 1857, p. 582 and 584; 1859, p. 693.) 



119. GUANO. 



Guano consists of the partially decomposed excre- 

 ment of sea-birds. It contains a great many sub- 

 stances, some soluble, others insoluble in water. The 

 constituents upon which depend its important action 

 and application as a manure are: organic, chiefly 

 nitrogenized matters ; salts of ammonia ; phosphates, 

 especially phosphate of lime ; and salts of the alka- 

 lies. The amount of these constituents indicates the 



