174 Wisconsin Academy of Sciences, Arts, and Letters. 
puted. To the titrated portions some sodium bicarbonate was 
added and the amount of As 2 0 3 determined by titrating with N/10 
iodine, using starch T. S. as an indicator. The computations were 
based on the following reactions:— 
I. K 8 C 0 3 4- HOH = KOH + KHC 0 3 ) 
>- Phenolphthalein. 
II. 2 KOH + H 2 S0 4 = K 8 S0 4 + H a O ) 
III. 2 KHCO 3 + H 8 S0 4 = K 3 S0 4 -f 2 H 2 0 + 2 C0 2 Methyl orange. 
Titrating with phenolphthalein as an indicator gives one half of 
the carbonate. Then adding methyl orange, the remaining half of 
the carbonate (as bicarbonate) and any bicarbonate originally 
present is determined. Hence the quantity of acid consumed by 
the original bicarbonate is represented by the total used with 
methyl orange as the indicator (after neutrality has been reached 
with phenolphthalein), minus that used with the first indicator. 
The following table reveals the computed percentage of the sev¬ 
eral components of possible arsenites. 
As. 
. K. . 
H. 
0 . . 
Total. 
/OH 
As—OH 
> 
KH 3 As 2 0 5 
55.10 
14.37 
1.11 
29.40 
99.98 
As—OH 
NOK 
272.044 
As=0 
> 
KHAs 2 0 4 
59.01 
15.39 
0.39 
25.19 
99.98 
As—OH 
\OK 
254.028 
/OH 
As—OH 
^0 
As—OK 
K 2 H a As 2 0 5 
48.34 
25.21 
0.65 
25.78 
99.98. 
310.136 
\OK 
