140 D. L. Randall — Titration of Mer citrous Salts. 



table shows that when the titration is made without unneces- 

 sary delay after adding the acid, as was the case here, three 

 per cent of pure nitric acid, the amount used in the subsequent 

 experiments, has no appreciable effect on the estimation of 

 ferrous iron. 



In Table III are given the results of a series of determina- 

 tions of mercurous nitrate by the method described above. A 

 solution was prepared by dissolving the crystallized salt in water 

 containing enough pure nitric acid to present the formation of 

 basic salts. As an additional precaution a current of hydro- 

 gen, washed by alkaline permanganate and alkaline pyrogallol, 

 was passed for twelve hours through the solution to remove 

 nitrous acid. Measured portions of this solution, which was 

 standardized gravimetrically as given above, were diluted to 

 200 cm3 , further acidified with pure nitric acid, and titrated in 

 the manner already described. 











Table III 











Hg 2 (N0 3 ): 

 sol. 

 cm 3 . 



2 Dil. 

 cm 3 . 



HNO, 

 cm 3 . 



Approx. 



N/20 

 KMn0 4 



cm 3 . 



FeS0 4 = 

 cm 3 . 



:KMn0 4 

 cm 3 . 



KMn0 4 

 cm 3 , 

 final 



= Hg 

 grm. 

 found 



Hg 



grm. 



theory 



Error 

 grm. 



25 



200 



5 



49-99 



9-76 



10-64 



39-35 



•3586 



•3594 



— •0008 



25 



200 



5 



49-68 



9-50 



10-36 



39-32 



•3583 



•3594 



— •0011 



25 



200 



5 



49-73 



9-50 



10-36 



39-37 



•3588 



•3594 



— •0006 



25 



200 



5 



49-89 



9-67 



10-54 



39-35 



•3586 



•3594 



— •0008 



25 



200 



5 



H 2 SO, 

 1:1 



49-70 



9-50 



10-36 



39-34 



•3585 



•3594 



— •0009 



25 



200 



5 



50-29 



10-00 



10-90 



39-39 



•3589 



•3594 



-'0005 



In the last experiment sulphuric acid was added instead of 

 nitric acid, yet as the table indicates, without apparent effect on 

 the result. 



This investigation has shown : 



1. That mercurous sulphate and mercurous nitrate can be 

 readily estimated by potassium permanganate with a very fair 

 degree of accuracy. 



2. That ferrous salts can be successfully titrated in the pres- 

 ence of at least three per cent of nitric acid. 



In closing the writer gratefully acknowledges the sugges- 

 tions of Dr. R. G. Van Name which led to this investigation. 



