402 Palmer — Application of Potassium, Ferricyanide 



The procedure was, in general, the same as in the determina- 

 tion of arsenic, except that it was found unnecessary to remove 

 the antimony before titrating witli permanganate. At least 

 five times as much potassium ferricyanide as theoretically 

 necessary was added in solution, and about 25 cubic centimeters 

 of a 20 per cent solution of potassium hydroxide. After stand- 

 ing a few minutes, the solution was strongly acidified with 

 dilute sulphuric acid and titrated with permanganate. The 

 results are given in Table III. 









Table III. 















Vol. 









Sb 2 3 







of 



Sb 2 3 







taken '. 



£ 3 FeC 6 N 6 



KOH 



sol. 



found 



Error 





grm. 



grm. 



grm. 



cm 3 . 



grm. 



grm. 



(1) 



0*0986 



8 



4 



100 



0-0989 



+ 0-0003 



(2) 



0-0986 



4 



4 



75 



0-0984 



-0-0002 



(3) 



0986 



2 



4 



75 



0-0984 



— 0-0002 



(4) 



0-0986 



4 



4 



150 



0-0984 



— 0-0002 



(5) 



0-0986 



4 



4 



75 



0-0984 



-0-0002 



(6) 



0*0493 



4 



4 



75 



0-0495 



+ 0-0002 



(?) 



0-0493 



4 



4 



75 



0-0497 



+ 0-0004 



(8) 



0-0493 



4 



4 



75 



0-0495 



+ 0-0002 



(9) 



0-1479 



4 



4 



75 



0-1482 



+ 00003 



(10) 



0-1479 



4 



4 



75 



0-1477 



— 0-0002 



(11) 



0-1479 



4 ■ 



4 



75 



0-1476 



— 0-0003 



(12) 



0-1971 



8 



8 



125 



0-1972 



+ 0-0001 



Determination of Tin 



Definite portions of metallic tin were accurately weighed out 

 and dissolved in concentrated hydrochloric acid; it was found 

 necessary to perform this operation in the cold, and to keep an 

 atmosphere of hydrogen over the liquid during solution of the 

 tin, as under other conditions results lower than the theoretical 

 were obtained, indicating that the stannous salt had been par- 

 tially oxidized by the air or by dissolved oxygen. When the tin 

 was completely dissolved, a solution containing at least five times 

 as much potassium ferricyanide as theoretically necessary was 

 added, and enough of a solution of potassium hydroxide to 

 completely dissolve the precipitated stannic acid, the two solu- 

 tions of ferricyanide and potassium hydroxide having been pre- 

 viously mixed. The stannic salt was removed by the addition 

 of about ten grams of ammonium sulphate, and warming to 

 50° or 60°, under which conditions the tin was completely pre- 

 cipitated. After it had settled, the precipitate was filtered off 

 on asbestos, under gentle pressure, and washed with a 10 per 

 cent solution of ammonium sulphate. The filtrate was strongly 

 acidified with sulphuric acid, and titrated with permanganate 



