GUANO. 235 



amounts, in good (undried) guano ; to only 1 or 2 per 

 cent. 



VII. The filtered hydrochloric solution is mixed 

 with a slight excess of ammonia. The precipitate thus 

 produced consists almost entirely of phosphate of lime. 

 It is filtered off, washed, dried, and ignited ; its quan- 

 tity in good guano amounts to 20 or 25 per cent. 



VIII. The filtrate from this precipitate should fur- 

 nish only slight indications of lime on addition of 

 oxalic acid ; but if the guano be adulterated with chalk, 

 this reagent will produce a very considerable precipi- 

 tate. This solution ought therefore to contain only the 

 alkaline salts, amounting to 5 or 10 per cent, of the 

 original undried guano. In order to determine them 

 directly, which is generally unnecessary for practical 

 purposes, the solution must be mixed with some more 

 chloride of ammonium, and evaporated to dryness; 

 the residue is heated to volatilize the excess of chloride 

 of ammonium, and to convert the sulphates into chlo- 

 rides, weighed, and farther treated as in No. 4. 



IX. The aqueous solution, which was obtained in 

 the lixiviation-test (IV.), and of which a fresh quantity 

 may be prepared so as to be saturated, has a brown 

 color and a saline taste. When evaporated it evolves 

 ammonia, emits a urinous odor, and leaves a brown 

 crystalline mass, consisting chiefly of sulphates of 

 potassa and soda, chloride of ammonium, oxalate and 

 phosphate of ammonia. This solution exhibits the 

 following reactions : 



When mixed with hydrate of potassa, it smells 

 strongly of ammonia. 



With chloride of ammonium, ammonia, and sulphate 

 9f magnesia, it gives an abundant pulverulent precipi- 

 tate or phosphate of magnesia-ammonia. 



When acidified with acetic acid and tested with 

 chloride of calcium, it gives a copious precipitate of 

 oxalate of lime. 



