436 W. A. Drushel — Potassium as the Cobalti-ni1i-it< . 



separated out and the color of the solution darkened. At this 

 point 5 cmS to 25 cma of sulphuric acid (1:7) were added, and 

 the solution, after stirring, was allowed to stand a few minutes. 

 Then a measured amount of standard oxalic acid, containing 

 50 cm3 strong sulphuric acid per liter, was run in from a burette, 

 taking care to add an excess.. The temperature was maintained 

 a little below the boiling point until the solution became color- 

 less and -the manganese hydroxide had completely dissolved. 

 It was then titrated to color by permanganate in the usual 

 manner. From the whole amount of permanganate used the 

 permanganate equivalent of the oxalic acid used was subtracted 

 and the remainder multiplied by the factor calculated for the 

 strength of permanganate used, 0*000856 being the factor for 

 strictly ~ potassium permanganate. 



To make the \- oxalic acid solution, exactly 7*1066 grm. of 



10 •> ° 



pure recrystallized ammonium oxalate were dissolved in about 

 700 cm3 of cold distilled water contained in a liter flask. To 

 this solution were then added 50 cm3 of strong sulphuric acid. 

 The contents of the flask were cooled to 15° C. and made up 

 to the mark with distilled water. The potassium permanga- 

 nate solution was made approximately decinormal and stand- 

 ardized in the usual way. This standard was checked by 

 standardizing under conditions as nearly as possible like those 

 under which the solution was used. A measured portion was 

 diluted ten times, heated nearly to boiling, acidified with dilute 

 sulphuric acid and allowed to stand a few minutes. It was 

 then bleached with a measured amount of oxalic acid, using it 

 in slight excess, and titrated to color. The two methods 

 agreed very well, the difference in permanganate seldom being 

 greater than one-tenth to two-tenths of a cubic centimeter in 

 25 cm \ 



Table II. 



No. 

 1. 

 2. 

 3. 

 4. 

 5. 

 6. 



^- 

 /. 



8. 

 9. 



K 2 taken 

 AsKCl 



grm. 



0-0237 

 0-0237 

 0-0354 

 0-0474 

 0-0048 

 0-0024 

 0-0005 

 0015 

 0-0355 



KoO found 



Error in K 2 



Gravi- 



metrically 



grm. 



0-0240 

 0-0243 

 0-0359 

 0-0478 

 0-0048 

 0-0024 



Volu- 



metrically 



grm. 



00238 

 0-0242 

 0-0355 

 0-0471 

 0-0050 

 0-0023 

 0-0006 

 0-0017 

 0-0355 



Gravi- 



nietrically 

 grm. 



0-0003 + 

 0-0006 + 

 0-0004 + 

 0-0004 + 

 0-0000 + 

 0-0000 + 



In the first six experiments of this series th 

 was dried at 115° C. and weighed. It was then 



Volu- 



metrically 



grm. 



0-0001 + 

 0-0005 4- 

 0-0000 + 

 0-0003 — 

 0-0002 + 

 O'OOO L — 

 0-0001 + 

 0-0002 + 

 0-0000 + 



e precipitate 

 treated with 



