PRACTICE XXV 



DETERMINATION OF TOTAL PHOSPHORUS IN FERTILIZERS 



Each group of students will work upon one of the following 

 materials : 1 



1. Bone ash. 5. Raw rock phosphate. 



2. Raw bone meal. 6. Acidulated rock phosphate. 



3. Steamed bone meal. 7. Double superphosphate. 



4. Acidulated bone meal. 8. Basic slag phosphate. 



For materials containing more than 9 per cent of phosphorus use 

 1 g. ; for lower percentages use 2 g. Ignite in a crucible to destroy 

 organic matter when present. Transfer to a beaker and digest in 

 15 cc. of dilute nitric acid, using a gentle heat. Transfer to a 250-cc. 

 measuring flask, cool, and dilute to exactly 250 cc. Mix well, trans- 

 fer to a dry bottle, and let settle. Measure 25 cc. into a beaker and 

 determine phosphorus according to the directions given in Practice 

 XX, using 35 cc. of the ammonium molybdate solution. 



cc. HXO 3 cc. KOH to mg. P % P Pounds 



used dissolve per ton 



ppt. 



Av 



Calculate the results obtained, and with these record the results 

 obtained by three members of each group, as indicated in the table 

 on the following page. Value phosphorus in 1, 5, and 8 at 3 cents ; 

 in 2 and 3 at 10 cents ; and in 4, 6, and 7 at 12 cents per pound. 



1 In addition the student may collect and analyze a sample of some phosphatic 

 material which may be of special interest to his home community. (Sample a ton or 

 a carload of bone meal or phosphate when bought in the neighborhood, by taking a 

 teaspoonful from each of 100 different places in the lot.) 



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