76 AGRICULTURAL ANALYSIS 



* 



ficultly soluble residue into solution, with addition of hydrochloric 

 acid, or of potassium chlorate, to destroy organic matter present. 

 Dilute the solution to a definite volume and determine the phos- 

 phoric acid in a measured quantity thereof, as directed under (a) 

 2; if hydrochloric acid or potassium chlorate be applied in the 

 preparation of the solution, however, the determination of the 

 phosphoric acid must not be made till the measured quantity 

 has been repeatedly evaporated to dryness with concentrated nitric 

 acid. 



2. In Bone-meal. Destroy organic matter in five grams of the 

 sample by ignition, dissolve the residue in nitric acid, filter from 

 the insoluble residue, dilute the filtrate to half a liter, and deter- 

 mine the phosphoric acid as directed under (a) 2 in an aliquot 

 part containing about one-tenth gram phosphoric pentoxid. 



3. In Fish-guano (and other fertilizing materials of organic 

 origin). The organic matter cannot here be removed by sim- 

 ple ignition, as in this way a loss of phosphorus may take place ; 

 it is therefore destroyed either in the wet way by nitric acid and 

 potassium chlorate, or in the dry way by fusion with a mixture of 

 potassium nitrate and sodium carbonate, otherwise the procedure 

 is as in (b) I. 



4. In Mineral Phosphates. Determine the phosphoric acid in 

 a solution obtained by nitric acid ; organic matter if present is 

 destroyed preferably in the wet way. 



5. In Basic Slag. Dissolve 10 grams of powdered slag by 

 treating it with 100 cubic centimeters of hot fuming hydrochloric 

 acid; wash the solution into a graduated half liter flask, fill to 

 the mark, shake well, and filter. Determine the phosphoric acid 

 in 25 cubic centimeters of the clear filtrate, according to (a) 2, 

 after having first, however, evaporated the solution to dryness 

 and then at least three times evaporated the residue to dryness 

 with concentrated nitric acid. 



83. Method Employed by the Royal Experiment Station of Hol- 

 land. A. Soluble Phosphoric Acid. The necessary reagents 

 are: 



(i) Molybdate solution, made by dissolving 150 grams of am- 



M Methoden van Onderzoek aan de Rijkslandbouwproefstations, 1893 : 4. 



