PRACTICE XXII (CONTINUED) 



3. Total Phosphorus. 



Determine as directed in Practice XXI, reserving the filtrate from 

 the ammonium hydroxid precipitate for the calcium and magnesium 

 determinations. 



cc. HXO 8 cc. KOHto mg. P %P Pin 



used dissolve '2 million 



ppt. of soil 



Av. .. 



4. Total Calcium. 



Concentrate the filtrate and washings from the ammonium hydroxid 

 precipitate in 3 to about 50 cc. If upon adding a few drops of ammo- 

 nium hydroxid a precipitate of aluminum appears, filter, wash, and 

 again concentrate to about 50 cc. Add a few drops of ammonium 

 hydroxid and enough ammonium oxalate solution to precipitate all 

 the calcium and to transform the magnesium from chloric! into oxa- 

 late. Digest two hours on the water bath, filter, wash with hot water 

 iintil free of chlorids, dry, and ignite in a weighed crucible over a 

 Bunsen burner, finishing to a constant weight over the blast lamp. 



Weight of crucible + CaO 



Weight of crucible 



Weight of CaO 



Weight of Ca 



Per cent Ca 



Av. per cent 



Ca in 2 million of soil 



5. Total Magnesium. 



Concentrate the filtrate and washings from 4 to about 50 cc., cool, 

 add a few drops of ammonium hydroxid, precipitate the magnesium 

 by adding slowly, while stirring, microcosmic salt in excess, add 10 cc. 

 of ammonium hydroxid, cover, and let stand over night. Filter, wash 

 with dilute ammonium hydroxid (1 part of ammonium hydroxid of .96 

 sp. gr. to 4 parts of water), dry, and ignite in a weighed crucible over 

 a Bunsen burner, finishing to a constant weight over the blast lamp. 



Weight of crucible + Mg P 2 O 7 



Weight of crucible 



Weight of Mg 2 P 2 O 7 



Weight of Mg 



Per cent of Mg 



Av. per cent 



Mg in 2 million of soil 



45 



