538 
IOIWA ACADEMY OF SCIENCE Vol. XXIV, 191' 
The two precipitates above mentioned were then prepared in 
larger quantities, and after careful washing and drying were 
further identified by analyses for nitrogen. 
Substance 
Nitrogen 
Found 
Calculated 
Benzidine sulfate 
9.61 
9.93 
9.53 
Benzidine selenate 
8.40 
8.51 
8.34 
In order to determine how nearly quantitative was the precipi- 
tation of selenic acid, a stock solution of the sodium selenate was 
prepared by dissolving one gram of the crystalline substance in 
100 cc. water. Portions of 10 cc. each of this solution were used 
for the determinations given below, which were carried out in 
the usual way, using both the benzidine and the barium chloride 
methods. Parallel determinations were made with a similar so- 
lution of sodium sulfate. 
Sodium Sulfate 
Benzidine 
BaSO, 
SO, 
Sulfate 
so 4 
Found 
Calc. 
Found 
Calc. 
.1289 
.0531 
.1552 
.0528 
.1288 
.0531 
.1548 
.0527 
Sodium 
Selenate. 
Benzidine 
BaSe0 4 
SeOj 
Selenate 
SeO, 
Found 
Calc. 
Found 
Calc. 
.0749 
.0383 
.0829 
.0360 
.0749 
.0383 
.0832 
.0362 
.0821 
.0357 
.0819 
.0356 
From the above data it will be seen that sulfate determined 
as benzidine sulfate agrees fairly well with that determined as 
barium sulfate, as has been claimed by other investigators. How- 
ever benzidine selenate, prepared here for the first time, is not 
precipitated as completely as the barium selenate. The average > 
of the four determinations shows that under the conditions of 
the experiment about 94 per cent of the selenate is precipitated 
by benzidine, assuming that the precipitation of barium selenate 
is quantitative. In the presence of dilute hydrochloric acid, 
tellurates give no precipitate with benzidine. 
Chemistry Section, 
State College. 
