Langenhan—The Arsenical Solutions. 
145 
B. Action of Alkalies on Arsenous Acid. 
Leaving out of consideration the diarsenous acid, 16 as well as 
other possible polyarsenous acids, it is quite apparent 
1.) That metarsenous acid is monobasic and with metals may be 
supposed to form the simple metarsenites: 
As 
\0—IT 
Metarsenous acid 
As 
\(J_M 
Metarsenites 
2.) That orthoarsenous acid is tribasic and may be expected to 
form three types of orthoarsenites, viz.: 
/OH 
As—OH 
\OH 
/OM' 
As—OH 
\OH 
/OM' 
As—OM' 
\OH 
/OM' 
As—OM' 
N OM' 
o—Arsenous acid Mono-metal 
dihydrogen 
orthoarsenite 
Di-metal Tri-metal 
monohydrogen orthoarsenite 
orthoarsenite 
This leaves out of consideration, for the time at least, the possi¬ 
bility of the re-arrangement of the atoms of the orthoarsenous acid 
molecule made possible by a change of valence, such as that of the 
phosphorus, from three to five and the salts of the new ic acid. 
As—H 
\OH 
\()H 
ic Isomer of o—arsenous acid 
Which of the above salts are formed depends, in part at least, 
on the ratio of acid and alkali. Presumably a mixture, not a single 
compound results. As to which may dominate in the equilibrium 
resulting from a given formula for preparation need not be con¬ 
sidered here, but will receive such attention as seems desirable, 
under the study of the pharmaeopoeial formulas in use. 
18 Pyroarsenites have also been prepared by Stavenhagen, 1. c. 
/OH 
As—OH 
\OH 
o—Arsenous acid 
10—S. A. L. 
