PRACTICE XXXI (CONTINUED) 



2. Calcium and Magnesium. 



Determine these in the filtrate from the ammonium hydroxid 

 precipitate in 1, according to the directions given in 4 and 5, 

 Practice XXII. 



Weight of crucible + CaO 



Weight of crucible 



Weight of CaO 



Weight of Ca 



Per cent of Ca 



Av. per cent 



Ca in 2 million of soil 



Weight of .crucible + Mg 2 P 2 7 



Weight of crucible 



Weight of Mg 2 P 2 7 



Weight of Mg 



Per cent of Mg 



Av. per cent 



Mg in 2 million of soil 



3. Potassium. 



Evaporate 100 cc. of Solution A to complete dryness in a porcelain 

 dish on the water bath. Ignite gently "over a Bunsen burner at a 

 dull red heat, add a little hot water, and grind very fine with the 

 blunt end of a glass rod. Add more water and digest thirty minutes 

 on the water bath, filter, wash thoroughly with hot water, acidify 

 with a few drops of hydrochloric acid, and concentrate on the water 

 bath with 1 cc. of platinic chlorid solution to a sirupy consistency. 

 Complete the determination as indicated in 6, Practice XXII. 



Weight of dish + K 2 PtCl 6 



Weight of dish 



Weight of K 2 PtCl 6 



Weight of K 



Per cent of K 



Av. per cent 



K in 2 million of soil 



68 



