268      WET  METHOD  OF  REDUCING  CHLORIDE  OF  SILVER. 
If,  however,  previous  to  the  addition  of  the  iron  salt  a  little 
phosphoric  acid  be  added,  no  coloration  takes  place  until  the 
whole  of  such  acid  has  first  been  removed  in  the  form  of  per- 
phosphate  of  iron.  In  order  for  this  latter  experiment  to  succeed 
perfectly,  the  iron  should  be  combined  with  an  acid  that  in  the 
free  state  has  not  the  power  of  dissolving  perphosphate  of  iron, 
— with  acetic  acid,  for  instance.  The  presence  of  a  minute 
quantity  of  hydrochloric  acid  would  tend  to  keep  the  perphos- 
phate in  solution,  and  coloration  more  or  less  would  consequently 
ensue. 
According  to  this  view,  phosphoric  acid  is  the  only  acid  that 
can  be  relied  on  for  the  preservation  of  syrup  of  iodide  of  iron, 
and  my  first  impression  as  to  the  utility  of  sulphuric  acid  could 
only  have  been  true  in  a  very  limited  sense.  In  the  long  run,  it 
could  not  have  been  otherwise  than  harmful. — London  Pharm. 
Journ.,  March,  1868. 
ON  A  WET  METHOD  OF  REDUCING  CHLORIDE  OF  SILVER. 
By  Dr.  Graeger.* 
There  are  many  methods  of  reducing  chloride  of  silver  with 
which  we  are  acquainted,  but  the  majority  of  them  are  surround- 
ed by  difficulties  of  some  kind  or  another  ;  either  the  silver  re- 
covered is  not  perfectly  pure,  or  the  manipulation  of  the  process 
is  attended  with  serious  loss,  or  it  is  impossible  for  the  whole  of 
the  chloride  to  be  reduced  at  one  operation.  Now,  as  the  re- 
duction of  chloride  of  silver  is  an  operation  which  has  very  fre- 
quently to  be  performed,  a  method  whereby  these  difficulties  are 
overcome  will  be  welcomed  with  pleasure ;  and  so  often  have  I 
felt  the  shortcomings  of  the  methods  at  present  employed,  that 
it  has  always  been  my  constant  endeavor  to  discover  a  better  and 
more  serviceable  mode  of  proceeding.  In  making  my  inquiries, 
I  have  always  had  in  view  the  advisability  of  seeking  for  a  wet 
method  of  reduction,  as  I  regarded  the  same  as  the  easiest  man- 
ner of  working,  and  involving  less  loss  of  material.    The  reduc- 
*  Neues  Jahrbuchfur  Pharmacie.  We  abridge  the  translation  given 
in  the  Photographic  News. 
