404 Gooch and Scoville—Reduction of Selenie Acid, ete. 
the sulphuric acid is also small, the reduction of the selenic 
acid and the evolution of the bromine progress slowly; and 
when the amount of bromide is small while that of the acid 
is comparatively large, the interval of colorlessness is prolonged. 
The proportions which we found best in handling 0°25 grm. 
of selenic acid, or less, are an initial volume of 60 em® con- 
taining 20 cm* of sulphuric acid of half-strength with 1 grm. 
of potassium bromide. Under these conditions we find, as in 
experiments (4) and (5) of the previous table, that the reduc- 
tion is almost theoretically exact when the distillation is con- 
tinued until the re-coloration of the boiling liquid is distinctly 
recognizable; and this point corresponds in practice very 
closely to a concentration of volume to 35 em*. In the follow- 
ing table are gathered the results of further experiments in 
which these conditions of action were preserved : 
SeO; taken H.SO, of KBr Initial Final SeO; 
as H,SeO,. half-strength. taken. volume. volume. calculated. Error. 
grm. em’, prm Wien, em', grm. grm. 
0°0590 20 1 60 35 0°0588 0°0002 — 
0°0590 20 1 60 30 0°0591 0°0001 + 
0°0614 20 1 60 35 0°0616 0°0002 + 
0:0614 20 i 60 390 0°0607 0°0007 — 
0°1180 20 1 60 35 071177 0°0003 — 
0°1180 20 1 60 395 0°1180 0:0000 
0°1534 20 1 60 35 0°1527 0°0007 — 
0°2349 20 1 60 35 0°2350 0°0001 + 
It is plain from these results that, if the conditions of action 
which we have indicated are observed, the reduction proceeds 
with regularity sufficient to warrant the use of the reaction as 
an analytical process. 
