258 Gooch and Reynolds—Reduction of the Acids, ete. 
when the free iodine is not removed from the sphere of action 
as it is liberated. In the distillation process the case is other- 
wise, and there is no reason to anticipate that the determina 
tion of selenic acid should present greater difficulty than is 
encountered in treating selenious acid under similar circum- 
stances. The experiments of Table IV, in which selenie acid 
(obtained by oxidizing known amounts of selenium dioxide by 
means of potassium permanganate in the manner described in 
a previous paper from this laboratory)* is treated according to 
the distillation method outlined above for the determination of 
selenious acid, show that this expectation is realized, and that 
the analytical results are fairly good. 
Tasie LV. 
HCl in Total] 
SeO; KI in flask. volume Time SeO; 
taken. flask. (Sp. gr.1:20) boiled. in found. Error. 
erm. germ. em® em* minutes. grm. erm. 
0'0593 1 3) 60 5 0°0593 0°0000 
0'0593 1 9) 60 5 ~ 0°0591 ~ 0°0002 — 
0'0593 3 5 60 10 0°0596 0:0003 +4 
0°1779 3 3) 60 10 0°1769 0:0010— 
0°1779 3 3) 60 10 0°1780 0°0001+ 
0°1779 3 5 60 10 0°1764 0°0015 — 
In conelusion, it is plain that while the simple contact of 
solutions of selenious acid or selenic acid and potassinm iodide 
acidified with hydrochloric acid does not determine the libera- 
tion of the full amount of iodine which would be expected if 
selenium, iodine and water were the sole produets of action, it 
is possible to bring about such action with a close approxima- 
tion to completeness, when the amounts of selenium present 
are not too large, by submitting such mixtures to distillation. 
We prefer, in applying the reaction to analytical purposes, to 
work with the apparatus and under the conditions described— 
treating, preferably, not more than 0:2 grm. of the selenium 
oxide, using from 1 grm. to 3 grm. of potassium iodide in the 
distilling-fask with 5 cm* of strong hydrochloric acid in a 
total volume of 60 cm® and continuing to boil for ten minutes. 
* Gooch and Clemens, this Journal, 1, 51. 
