144 Wisconsin Academy of Sciences, Arts , and Letters. 
H 
As + OH 
\()H 
Metarsenous acid 
/OH 
As—OH 
\OH 
Ortho-arsenous acid. 
For a better understanding of the chemical possibilities of prod¬ 
ucts obtained upon the evaporation of the solution of the arsenites, 
the following condensation products of ortho-arsenous acid with 
itself may be referred to. 
/OH 
As—OH 
\OH 
—h 2 o 
/OH 
As-OH 
\()H 
Ortho-arsenous acid 
w? r 
/OH 
As—OH 
^O 
As—OH 
\OH 
Di-arsenous acid (tetra basic) 
Still another dehydration reaction may be indicated by the fol¬ 
lowing formulas: 
HO 
OH 
As 
O 
-H s O 
HO — As 
OH 
OH 
As 
As 
OH 
O 
Uiarsenous acid (dibasic) 
A trioxide of arsenic resulting upon complete dehydration of 
this dibasic diarsenous acid which, however, is different structur¬ 
ally, hence in its properties, from the compound with which we 
started out, readily follows: 
O 
.As\ 
OH ' 
OH 
'As^' 
O 
H 2 0 
O 
As 
<To 
As 
Diarsenous acid (dibasic) 
Diarsenous acid anhydride. 
The possibilities of other hydration products of arsenic trioxide 
need not here be considered. 
15 Salts of this acid have been prepared by Stavenhagen, 1. c. 
