PRECIPITATION  OF  PROTOCHLORIDE  OF  ANTIMONY.  465 
protochloride  of  antimony,  but  at  each  operation  it  was  neces. 
sary  to  increase  the  quantity  of  liquid  employed. 
The  explanation  given  by  the  author  of  these  curious  reactions 
is  as  follows ; — Protoxide  of  antimony  is  one  of  those  compounds 
placed  at  the  extreme  limit  of  acids  and  bases,  the  parts  of 
which  it  can  assume  by  turns.  In  presence  of  muriatic  acid  it 
will  exert  a  property  in  antagonism  with  the  latter,  and  will  be 
basic.  In  the  presence  of  water,  on  the  contrary,  it  will  change 
its  part,  and  become  acid  in  relation  to  this,  which  will  act  as  a 
base.  Now  the  acidity  or  basicity  of  Sb2  O3  will  depend  on  the 
proportions  of  water  or  muriatic  acid  which  it  encounters. 
When  the  acid  predominates,  it  will  become  basic ;  by  making 
the  water  predominate,  Sb2  O3  will  be  converted  into  an  acid. 
A  new  addition  of  C1H  will  again  change  the  office  of  Sb2  O3, 
and  so  on, 
A  mixture  of  100  parts  of  water  and  15  parts  of  muriatic 
acid  with  16  equivs.  of  water,  will  keep  protochloride  of  anti- 
mony in  a  solution  which  is  on  the  brink  of  precipitation ;  the 
addition  of  a  drop  of  water  whitens  it,  and  a  drop  of  acid  re- 
stores its  limpidity.  These  proportions  of  water  and  acid  are? 
therefore,  as  it  were,  the  measure  of  their  respective  forces  as 
chemical  agents  Ohem.  Gaz.*  July  1,  1856,  from  Comptes 
Mendus,  May  5,  1856. 
30 
