368 
IOWA ACADEMY OF SCIENCE Vor. XXIX, 1922 
the new solution of titanous sulfate was also treated with the 
same solution of permanganate used in Tables I and II, running 
the titanium solution into the permanganate. The results are 
seen in Table V. 
TABLE V 
DIRECT ELECTROMETRIC TITRATION OF NEW TITANOUS 
SULFATE SOLUTION WITH PERMANGANATE 
KMnOi cc. 
TkCSOUs cc. 
TkCSOOa 0.05 N times 
42.46 
43.90 
0.9672 
37.20 
38.75 
0.9600 
36.09 
37.55 
0.9611 
49.25 
50.94 
0.9668 
31.37 
32.62 
0.9617 
Average 0.96336 
The average result with permanganate is, doubtless largely by 
accident, almost precisely the same as the averages obtained with 
dichromate, and the fact makes iit extremely probable that both 
methods are accurate. Any question in this respect is settled by 
the work of Jatar 7 which proved that dichromate and titanous 
chloride act upon each other quantitatively, the valence of chro- 
mium changing from 6 to j 3 and that of titanium from 3 to 4; in 
fact, he used titanous chloride for standardizing dichromate and 
employed a mixture of ferrous iron and thiocyanate as external 
indicator. It would seem that either oxidant may confidently be 
used either directly or through the medium of ferric iron for the 
determination of titanium by the electrometric method. 
The sharp change in potential from a slight excess of titanous 
ion to slight excess of permanganate is about 0.9 volt, and from 
a slight excess of titanous ion to an excess of dichromate ion 
about 0.6 volt, and as already indicated these facts may permit 
the determination in certain instances of 2 substances of quite 
different oxidizing or reducing power when present in the same 
solution; for example, titanous and ferrous ions with permanga- 
nate or dichromate, ferric ion and permanganate with titanous 
ion. We have made such titrations of mixtures, and that they are 
entirely practicable is best shown by the voltage curves in Fig. 1. 
Curve 1 shows the titration of a mixture of ferrous and titanous 
ion with permanganate; Curve 2 shows the titration of ferrous 
and titanous ions with dichromate ; Curve 3 is the reverse of Curve 
1 and shows the titration of ferric ion and permanganate with 
titanous ion; -Curve 4 is the reverse of 2 and illustrates voltage 
changes in titrating dichromate and ferric iron with titanous ion. 
7 Jatar, J. Soc. Chem. Ind., 27, 673 (1908). 
