234 8 119. 



FERTILIZERS. 



yelloAvisli-browii powder mixed with soft lumps of various 

 sizes, which, when broken, exhibit white veins on the 

 fractured surface, or sometimes a foliated crystalline ap- 

 j)earance. 



If a small quantity is heated with a few drops of dilute 

 nitric acid and the mixture is evaporated to dryness at a 

 gentle heat, a fine, purple-red colored residue is left, indi- 

 cating the presence of uric acid (§ 75). 



It gives a good reaction for ammonia wilh sodic hydrate 

 or lime. 



By digestion with water, about half is dissolved, form- 

 ing a dark-yellow solution; if tjie guano is poor, a light- 

 yellow solution is obtained. This solution gives the usual 

 reactions for ammonia, lime, magnesia, and sulphuric acid. 



It loses 60-70"!^ when ignited, and leaves a grayish- 

 white ash that evolves but little carbonic acid when treat- 

 ed with nitric acid, and leaves but from 1-3° | „ of matters 

 insoluble in acid, and contains 5-10" |y of fixed alkaline 

 salts. 



Baker guano^ and other phosphatlc guanos. — These 

 arc examined in the same manner as the Peruvian guano, 

 except that, since they contain but a very small propor- 

 tion of nitrogen and alkaline salts, the determination of 

 phosphoric acid alone answers for the estimation of their 

 agricultural value. This may generally be made by the 

 volumetric process. 



SUPERPIIOSPHAtES. 



119. These are generally mixtures of calcic sulphate, 

 calcic chloride, tricalcic phosphate, ferric phosphate, 

 monocalcic phosphate, organic matters containing nitro- 

 gen, .coal and water. 



Mix the sample well together, breaking up all the lumps 

 between the fingers or in the mortar. 



a. Water. — Desiccate 3-4 grms. for a considerable time 

 at 150-160° C. (§ 90). 



