444         PURE  SILVER,  FROM  ITS  ALLOY    WITH  COPPER. 
the  liquor,  when  filtered,  contains  phosphate  of  lime  and  phos- 
phate of  magnesia  in  solution.  The  same  is  the  case  if  water  be 
used,  from  which,  by  long  continued  boiling,  all  carbonic  acid  has 
been  expelled.  Water  was  filtered  for  several  months  through 
the  same  quantity  of  ground  bones,  constantly  taking  up  some 
of  the  phosphates  of  those  earths  whose  amount  even  seemed  to 
increase  as  the  organic  matter  of  the  bones,  by  its  continued 
contact  with  water  and  air,  was  putrified,  and  the  passed  water 
became  turbid  and  foetid.  These  facts  appear  to  be  not  without 
their  practical  value  for  agriculture,  as  the  earthy  phosphates 
of  the  bones,  without  artificial  preparation,  may  be  dissolved, 
and  thus  carried  to  the  ground,  probably  in  a  quantity  which  is 
just  necessary  for  the  functions  they  have  to  perform.  For  the 
use  of  ground  bones,  as  manure,  it  would  suffice  perhaps  to  pre- 
pare them  simply  by  keeping  them  during  the  summer  time 
moist  and  in  heaps. -—{Annalen  d.  Chem.  and  Pharm.,  April, 
1856,  p.  143.)  J.  M.  M. 
PREPARATION  OF  PURE  SILVER  FROM  ITS  ALLOY  WITH 
COPPER. 
By  Dr.  W.  Wicke. 
The  alloy  is  dissolved  in  nitric  acid,  the  excess  of  the  acid  ex- 
pelled by  boiling,  the  solution  diluted  with  water  and  the  oxides 
precipitated  by  an  excess  of  carbonate  of  soda  at  an  elevated 
temperature.  By  heating  the  carbonates  with  a  solution  of 
grape-sugar,  the  oxides  are  reduced,  the  oxide  of  copper  to  the 
sub-oxide,  the  oxide  of  silver  to  the  metal.  The  reduction  com- 
mences immediately,  but  the  boiling  must  be  continued  for  some 
time  to  insure  the  reduction  of  all  the  carbonate  of  silver.  The 
precipitate  is  filtered  ;  and  while  still  moist  treated  with  a  warm 
solution  of  carbonate  of  ammonia,  which  dissolves  the  copper, 
leaving  pure  silver  behind  ;  the  operation  is  continued  until  the 
carbonate  of  ammonia  ceases  to  assume  a  blue  color.  The  wash- 
ing may  be  done  by  decantation.  If  the  silver  is  not  wholly  re- 
duced, the  carbonate  of  ammonia  will  also  dissolve  carbonate  of 
silver.  I  have  boiled  with  grape-sugar  about  ten  minutes,  and  the 
ammoniacal  solution  was  free  of  silver. 
