Am.  Jour.  Pharm. 
July,  1899. 
Bismuth  Subgallate. 
33i 
solution  of  sodium  hydrate,  but  very  much  more  slowly  than  the 
bismuth  subgallate.  On  heating,  solution  is  much  more  rapidly 
effected,  but  this  may  be  due  to  the  hydrolising  influence  of  the 
fixed  alkali  on  the  tannic  acid,  converting  it  into  gallic  acid.  It 
must  be  stated,  however,  that  one  make  of  tannate  is  much  more 
readily  soluble  than  another.  This  may  be  due  to  a  difference  in 
the  composition  of  the  tannic  acid  employed. 
The  solubility  of  bismuth  subgallate  in  sodium  and  potassium 
hydrate  solutions  is  very  striking  and,  naturally,  the  question  is 
asked,  why?  On  recalling  to  mind  we  find  that  bismuth  subgallate 
is  not  the  only  bismuth  compound,  as  commonly  supposed,  possess- 
ing this  property;  bismuth  pyrogallate  is  just  as  readily 'soluble  in  the 
same  alkaline  solutions  and  otherwise  possesses  analogous  properties. 
Bismuth  subtannate  was  spoken  of  above.  We  have  a  similar  phe- 
nomenon in  the  case  of  bismuth  citrate  and  ammonium  hydrate, 
in  iron  and  ammonium  citrate  and  many  others. 
There  have  been  various  chemical  formulas  assigned  to  this  com- 
pound. H.  Causse1  found  in  his  investigation  that  the  salt 
lost  two  molecules  of  water,  or  9  per  cent.,  at  iOO°  C,  and  assigns 
to  it  the  formula  C((H2OHO20O2Bi  -f  2H20.  He  attributes  the 
yellow  color  to  the  saturation  of  the  phenol  function  of  the  acid.  Ac- 
cording to  the  above  results,  the  bismuth  subgallate  supplied  in  this 
country  is  quite  different  from  the  article  examined  by  Mr.  Causse, 
for  the  highest  amount  of  moisture  obtained  at  no°  C.  was  only 
5-56  per  cent.  Mr.  Causse,  however,  probably  worked  with  the 
crystalline  article  obtained  by  his  process,  yet  the  writer  of  this 
article  also  had  one  crystalline  product,  but  its  moisture  was  the 
lowest  of  any  examined.  There  are  some  reasons  for  thinking  that 
the  yellow  color  may  be  due  to  the  saturation  of  the  phenol  func- 
tion, for  instance,  bismuth  pyrogallate,  whose  formula  is  supposed 
to  have  the  following  configuration  : 
C„H,(01i), 
\ 
o 
I  >  Bi(OH) 
O 
/ 
C6H3(OH)2 
1  1893,  Comp.  rend.,  117,  232  ;  Chem.  Ztg.,  77,  276. 
