IF. A. Drushel — Potassium as the Cobalti-nitrite. 43 1 



permanganate by the method previously described. Experi- 

 ments 6, 7 and 8 show that very small amounts of potassium 

 may be estimated with a fair degree of accuracy. 



In Table III the effect of the presence of members of the 

 calcium group was investigated. Calcium and magnesium 

 apparently do not interfere, while barium and strontium tend 

 to give high results. 



Table III. 



CaCl 2 MgCl 2 , BaCl 2 , SnN0 3 ) 2 K 2 K 2 



taken taken found Error 



grm. grm. grm. grm. grm. grm. grm. 



0-0005 0-0007 0-0002 + 



0-0237 0-0234 0-0003 — 



0-0829 0-0824 0005 — 



0-5000 0-0711 0-0737 0-0020 + 



0-5000 0-5000 00474 0-0493 0-0019 + 



0-5000 00237 0-0251 0-0014 + 



0-0711 0-0713 0-0002 + 



The method itislj also be used in the presence of phosphoric 

 acid and is therefore applicable to the estimation of lv 2 in fer- 

 tilizers. In Table IV are the results obtained in nine fertili- 

 zers by the platinic chloride method and the cobalti-nitrite 

 volumetric method. In columns one and two are the duplicate 

 results obtained by two analysts of the Connecticut Agricul- 

 tural Experiment Station, and in column three are the results by 

 the volumetric method. The water-soluble phosphoric acid 

 present in these samples is given in the fourth column. 



Table IV. 

 K 2 in Mixed Fertilizers. 

 K 2 by platinum K 2 by vol. Water-soluble 



chloride method cobalti-nitrite meth. P 2 5 in sample 



1. 



0-2000 



0-2000 



2. 



0-3000 



0-5000 



3. 



0-5000 



1-0000 



4. 



0-5000 



roooo 



5. 



0-5000 



1-0000 



6. 



0-5000 



1-0000 



7. 



0-5000 



1-0000 



No. 

 1. 

 2. 

 3. 

 4. 

 5. 



per cent 



5-22 



6-53 



2-23 



8 68 



6-37 



6-08 



4-08 



4-62 



1-68 



per cent 

 5-18 

 6-56 

 2-24 

 8-64 

 6-42 

 6-13 

 4-02 

 4-66 

 1-67 



per cent 

 5-18 

 6-56 

 2-24 

 8 78 

 6-38 

 6-13 

 4-02 

 4-67 

 1-77 



per cent 



•16 



•10 

 •82 

 •94 

 •62 

 •61 

 •15 

 •43 

 •03 



Ten grams of the fertilizer were placed in a 500 om3 flask and 

 300 cm3 of water were added. The contents were boiled for 30 

 minutes and ammonia water was added to slight alkalinity. 

 Enough ammonium oxalate was added to precipitate all the 

 calcium and, after cooling, the solution was made up to the mark 

 on the neck of the flask and well shaken. The solution was 



