434 IF. .4.. Drushel — Potassium as the Gobalti-nitrite, 



Portions of a potassium chloride solution of known strength 

 wore treated with an excess of sodium cobalti-nitrite* and 

 filtered on perforated crucibles fitted with asbestos felts. The 

 precipitates were first washed with a 10 per cent acetic acid 

 solution, then once with water. In experiments 1 to 5 the 

 precipitate was decomposed by boiling with sodium hydroxide 

 and the nitrites estimated according to the method of Adie 

 and TVood, giving the results in the second column of Table 

 I. The cobaltic hydroxide filtered off on asbestos was reduced 

 by heating nearly to boiling in a measured amount of standard 

 oxalic acid containing a little sulphuric acid. The excess of 

 oxalic acid was estimated by titrating with standard potassium 

 permanganate, and from this the equivalent of the cobaltic 

 hydroxide in terms of permanganate was found by subtrac- 

 tion, giving the results in the third column of the table. In 

 experiments 6 to 10 the precipitated potassium salt together 

 with the crucible and asbestos felt, after stirring the precipitate 

 and felt loose from the crucible, was placed in a beaker con- 

 taining a* measured amount of standard permanganate, taking 

 care to use an excess, diluted to about ten times its volume 

 and heated nearly to boiling. After five to eight minutes, or 

 when the manganese hydroxide formed gave the solution a 

 dark color, it was acidified with 5 cm3 to 20 cm3 of sulphuric acid 

 (1 : 7). After a few minutes a measured excess of standard 

 oxalic acid was run iu from a burette, the temperature being 

 kept a little below the boiling point until the solution became 

 clear, and then titrated to color with permanganate. The 

 whole amount of permanganate used less the equivalent of the 

 oxalic acid used is the amount necessary for the oxidation of 

 the precipitate. The results are given in the fourth column. 







Table I. 









K.,0 



taken 



KMn0 4 used in 



titration of nitrites 



alter removal 



of cobaltic 



hydroxide 



KMn0 4 



equivalent 

 to cobaltic 

 hydroxide 



KMn©4 



used in 



direct 



titration 



No. 



grm. 



cm 8 . 



cm 3 . 



cm 3 . 



1. 



2 



0-0235 

 0-0235 

 0-0235 

 0-0353 



32-4 

 32-25 

 32-65 

 48-35 



2'5 





2-5 





3. 

 4. 





3-88 







5. 



0-0353 



49' 



3-95 







6. 



0-0235 











30- 



7. 



0-0235 











29-65 



8. 



0-0235 







' 



29-4 



9. 

 10. 



0-0353 

 0-0353 







43-65 

 44-4 











* Prepared according to the directions given by Adie and Wood loc. cit., also 

 given in Sutton's Yolumetric Analysis, 9th ed., p. 62. 



