246 
ON  TANNATE  OF  BISMUTH. 
suddenly  changes  to  a  deep  brown.  On  cooling  it  deposits  a 
substance  of  the  same  color,  which,  separated  by  filtration,  dried 
in  the  air,  and  dissolved  in  hydrochloric  acid  gives  a  mixture  of 
the  protochloride  and  perchloride  of  iron.  If  a  magnet  be 
brought  in  contact  with  the  brown  matter  when  dry,  it  is  found 
to  adhere,  showing  that  by  heating  a  solution  of  carbonate  of 
iron  magnetic  oxide  is  formed. 
The  preparation  of  an  aerated  chalybeate  water  is  very  simple. 
We  have  only  to  place  some  clean  pieces  of  iron  in  the  upper 
vessel  of  one  of  the  ordinary  gazogenes,  and  set  the  apparatus  in 
a  cool  place  for  48  hours,  by  which  time  a  liquid  is  obtained 
which  only  differs  from  the  before-mentioned  in  the  excess  of 
carbonic  acid  which  it  contains.  The  taste  is  sensibly  inky,  but 
it  is  not  at  all  disagreeable  to  drink. 
Two  experiments  have  been  made  to  determine  the  amount  of 
carbonate  of  iron  in  solution.  In  both  cases  a  quantity  of 
peroxide  was  found  corresponding  to  rather  more  than  half  a 
grain  of  the  protocarbonate  in  100  grammes  (3  oz.  It  drs.  13 
grs.)  of  the  water.  The  quantity  of  iron  in  the  water  may  be 
increased  or  diminished  by  leaving  the  two  in  contact  for  longer 
or  shorter  periods. — Jour,  de  Pharm.,  Jan.,  1860,  and  Chem. 
News,  Feb.  25th,  1860. 
ON  TANNATE  OF  BISMUTH. 
By  M.  Cap. 
Tannate  of  bismuth  has  been  introduced  in  France  as  a 
remedy  for  obstinate  diarrhoea.  It  is  prepared  by  first  precipi- 
tating the  oxide  of  bismuth  from  a  solution  of  44  parts  of  the 
crystallized  nitrate  by  means  of  an  excess  of  strong  caustic 
soda.  The  precipitate  is  collected  on  a  cloth  and  carefully 
washed.  It  is  then  triturated  in  a  mortar  with  29  parts  of  pure 
tannin.  The  magma  is  then  diluted  with  water,  the  whole  is 
thrown  on  a  cloth,  washed  and  then  dried  either  in  the  open  air 
or  in  a  slightly  heated  closet. 
The  salt  has  a  yellowish  appearance;  it  is  insoluble  and 
consequently  almost  tasteless  ;  it  is  easily  suspended  in  a  mucil- 
aginous vehicle,  in  syrup,  or  in  glycerine;  and  can  also  be 
administered  in  the  form  of  pills,  or  of  an  electuary. 
