330 W. A, Drushel—Cobalti-Nitrite Method. 



For the extraction of the alkalis 10 grin, of dry soil are 

 placed in an Erlenmeyer flask with 25 cra3 to 35 c,n3 of about 20 

 per cent, hydrochloric acid. The flask is thoroughly shaken 

 and a small funnel is hung in its neck to avoid too great a loss 

 of acid by evaporation. The contents of the .flask are digested 

 on the steam bath for 24 hours. 



From this point several methods for the final preparation of 

 the sample were tried with satisfactory results, given in the 

 table. Since duplicate estimations were to be made by the 

 gravimetric chlorplatinate method, for which it was necessary 

 to remove the iron, aluminum, calcium, magnesium, phosphoric 

 acid and ammonium salts, if present, from the soil extract, the 

 following general procedure was found to be most expeditious. 

 The soil extract was filtered through paper into an evaporating 

 dish and the residue was washed with boiling water until the 

 filtrate gave no reaction for chlorine with silver nitrate. The 

 filtrate was evaporated almost to dryness to remove the excess 

 of hydrochloric acid as far as possible. The residue was dis- 

 solved in about 200 cra3 of water and, after heating to boiling, 

 a little ammonium hydroxide and ammonium oxalate were 

 added. The mixture was boiled a minute, settled, filtered and 

 the precipitate was washed with hot water until a drop of the 

 filtrate give no chlorine reaction. The filtrate was concentrated, 

 transferred to a 200 c,n3 flask, cooled, and made up to the mark. 

 After thoroughly shaking, 50 cm3 aliquots were pipetted off for 

 the gravimetric and volumetric estimations. The aliquots were 

 evaporated to dryness in platinum dishes, and gently ignited 

 to remove the ammonium chloride. After cooling, the residue 

 was moistened with dilute sulphuric acid and again ignited, 

 gently at first and finally at the full heat of the Bunsen flame, 

 to remove the last trace of ammonium present as the sulphate, 

 and to destroy any organic matter which might be present. 



The residue for the gravimetric estimation was dissolved in 

 a little water and a few drops of hydrochloric acid over the 

 steam bath, and the estimation of the potassium was made 

 according to the modified Lindo-Gladding method. 



To dissolve the residues for the volumetric estimations a 

 little water and a few drops of acetic acid instead of hydro- 

 chloric acid were used. In the volumetric work approximately 

 -N"/5 potassium permanganate was used, 26*08 cm3 of permangan- 

 ate being equivalent to 50 cm3 of exactly N/10 oxalic acid. 

 From this ratio the factor for K 2 was found to be 0-001642. 

 In each case the potassium was precipitated as the cobalti- 

 nitrite by evaporating off with 10 cm3 of sodium cobalti-nitrite 

 prepared according to the method of Adie and Wood.* 



* Journ. Chem. Soc, lxxvii, 1076-80 (London). 



