332 W. A. Drushel—Cobalti-Mtrite Method. 



Summary. 



A weighed amount of dry soil is extracted with an excess 

 of hydrochloric acid over the steam bath. The excess of acid 

 is removed from the extract by evaporation. The bases which 

 might interfere w T ith the process are removed with sodium 

 carbonate or ammonium hydroxide and ammonium oxalate. 

 Ammonium salts and organic matter are removed by ignition. 

 The residue is dissolved in a little water and a few drops of 

 acetic acid, and the mixture evaporated with an excess of 

 sodium cobalti-nitrite to a pasty condition, stirred up with cold 

 water, and filtered upon asbestos in a perforated crucible. The 

 precipitated potassium sodium cobalti-nitrite is washed with 

 half -saturated solution of chloride, and treated with an excess 

 of permanganate in hot dilute solution. The color of the per- 

 manganate is destroyed by an excess of standard acidulated 

 oxalic acid, and the excess of oxalic acid titrated to color with 

 permanganate. 



