SYRUP  OF  IPECACUANHA.  143 
II.  Ferrocyanide  of  barium,  obtained  by  decomposing  a  hot 
solution  of  ferrocyanide  of  potassium  by  chloride  of  barium,  is 
very  sparingly  soluble  ;  it  is  precipitated  at  the  moment  when 
the  solutions  are  mixed,  in  the  form  of  small  yellow  crystals. 
In  this  state  it  still  retains  some  potassium,  from  which  it  may 
be  freed  by  boiling  with  a  solution  of  chloride  of  barium. 
By  mixing  together  in  the  cold  equivalent  proportions  of  the 
ferrocyanide  thus  purified  and  dilute  sulphuric  acid,  the  decom- 
position takes  place  instantaneously ;  sulphate  of  baryta  is 
thrown  down,  and  the  liquid,  which  acquires  a  green  color,  con- 
tains the  hydroferrocyanic  acid.  By  using  sulphuric  acid  of 
spec.  grav.  1-834,  diluted  with  5  or  6  times  its  volume  of  water, 
the  acid  isolated  presents  a  density  of  12°  to  15°  B. 
This  acid  cannot  be  concentrated  by  heat ;  to  obtain  it  directly 
in  a  state  of  greater  concentration,  less  water  may  be  employed 
in  its  preparation,  but  then  the  sulphate  of  baryta  would  be 
washed  with  more  difficulty.  The  acid  should  be  preserved  in 
well-stoppered  earthen  vessels. 
With  the  acid  thus  isolated  the  author  obtains  hydroferrocyanic 
acid  in  a  solid  state  and  perfectly  pure,  by  adding  an  excess  of 
concentrated  muriatic  acid  and  a  little  ether,  and  drying  the 
product  without  heat  in  presence  of  fragments  of  quicklmie. 
In  this  way  he  avoids  the  presence  of  the  chloride  of  potassium 
which  remains  mixed  with  the  acid,  when  ferrocyanide  of  potas- 
sium is  treated  by  the  same  agents. 
This  process  is  also  applicable  to  all  the  acids  which  are  now 
isolated  by  the  decomposition  of  their  lead-compounds  by  sul- 
phuretted hydrogen,  or  their  lime-compounds  by  sulphuric  acid, 
such  as  malic  acid,  phosphoric  acid,  &c  London   Chem.  Gaz. 
Nov.  1,  1858,  and  Dec.  15, 1858,  from  Comptes  Bendus, 
ON  SYRUP  OF  IPECACUANHA. 
By  Israel  J.  Gkaham. 
It  has  always  been  an  object  with  the  writer  in  the  prepara- 
tion of  this  syrup,  to  conduct  the  process  with  a  view  to  avoid 
any  possible  injury  which  might  arise,  during  the  prolonged 
