§ 118. GUANO. 233 



bonatc and 1 of nitre, fuse tho mixture carefully, dissolve 

 tlie residue in water, and evaporate the solution to dryness 

 on the water-bath ; treat this residue with hydrochloric acid 

 and water, as in eliminating silicic acid (§ 58, a, 1) ; filter, 

 add ammonia to the filtrate until it is in slight excess, then 

 acetic acid until the calcic phosphate precipitated by the 

 ammonia is dissolved; and then, without filtering out the 

 small amount of ferric phosphate, determine phosphoric 

 acid by the volumetric method. (Fresenius.) 



/. Complete analysis. — Treat a portion of the solution 

 obtained in c, or one obtained in like manner, after elimi- 

 nation of silicic acid, according to Scheme lY., § 94. 



fj. Solubility in water. — Heat 10 grms. of the powdered 

 guano with 200 c.c. of water, filter at once through a 

 weighed filter, Avash the contents of the filter with hot 

 water, as long as tlie water has any yellow color and 

 leaves a residue when evaporated ; dry and weigh the in- 

 soluble residue. Subtract the sum of the water and the 

 insoluble substance from the total weight of the gutuio, 

 and the remainder will be the soluble matter ; and, if the 

 insoluble residue is ignited and the ash weighed and sub- 

 tracted from the total amount of ash, the amount of solu- 

 ble non-volatile matters will be given by the remainder. 

 (Fresenius.) 



A. Uric acid. — Digest the part of the gunno that is in- 

 soluble in water with a weak solution of sodic hydrate ; 

 filter the mixture, precipitate the uric acid in the filtrate 

 with hydrochloric acid, and proceed as directed in § 75, 

 with the washing of the precipitate. 



^. Oxalic acid. — Expel the carbonic acid from a weigh- 

 ed portion of the guano with sulphuric acid, neutralize 

 the excess of acid with sodic hydrate entirely free from 

 carbonic acid, and estimate oxalic acid with sulphuric acid 

 and manganic binoxide (§ 69). 



h. Marks of a good Peruvian guano.— It forms a loose, 



