234 
ON  THE  LIQUOR  POTASSiE  ARSENITIS. 
stance ;  but  failing  in  that,  I  evaporated  it  carefully  to  dryness, 
and  made  an  analysis  of  the  substance  dried  at  100°  C.  This 
yielded  73.976  per  cent,  of  arsenious  acid.  The  percentage  of 
arsenious  acid  contained  in  a  substance  of  the  formula  KG,  As03, 
presuming  that  such  is  the  composition  of  arsenite  of  potash, 
would  be  67.757 — my  substance,  therefore,  contains  a  little  more 
than  six  per  cent,  of  arsenious  acid  in  excess,  as  expressed 
below : — 
73.976  percentage  of  As03  in  substance  examined. 
67.757  percentage  of  As03  in  the  (KO,  As03). 
6.219  excess  of  arsenious  acid. 
I  tried  to  get  rid  of  this  excess  of  arsenious  acid,  by  treating 
the  substance  with  cold  water,  filtering  from  the  undissolved 
arsenious  acid,  evaporating  to  dryness,  again  treating  with  cold 
water,  and  repeating  this  until  it  dissolved  in  water,  without 
leaving  a  residue  ;  but  I  found,  on  analysis,  that  it  had  made 
little  difference  in  the  percentage  of  the  arsenious  acid. 
Another  experiment  was  made  by  boiling  carbonate  of  soda 
(NaO,  C02)  with  excess  of  arsenious  acid,  treating  it  precisely 
in  the  same  manner  as  the  compound  with  potash  ;  but  I  was 
equally  unsuccessful  in  obtaining  crystals  or  a  crystalline  sub- 
stance. 
This  substance,  dried  at  100°  C.  was  found  to  contain  82.382 
per  cent,  of  arsenious  acid.  The  percentage  in  a  compound  of 
the  formula  (NaO,  As03)  would  be  76.1538  : 
82.3820  percentage  of  As03  in  substance  examined. 
76.1538  percentage  of  As03  in  (NaO,  As03). 
6.2282  excess  of  arsenious  acid. 
As  exhibited  above,  the  soda  compound  with  arsenious  acid 
had  more  than  six  per  cent,  of  acid  in  excess,  just  as  the  com- 
pound with  potash.  I  considered  it  advisable  to  make  a  complete 
analysis  of  this  substance  ;  the  results  were  as  follows  : — 
82.382  per  cent,  of  arsenious  acid. 
17.409  per  cent,  of  soda. 
99.791 
