36  Nitrate  of  Silver  containing  Gold:  {Km-J™^vm~ 
possible  detail,  as  it  is  just  the  omission  to  do  this  that  has  caused  so 
many  confusing  and  incorrect  statements  to  appear  in  our  text-books. 
The  tests  described  are  remarkably  liable  to  failure  when  the  conditions 
are  slightly  varied.  This  is  notably  the  case  with  the  reactions  with 
solutions  of  soda,  a  change  of  temperature  or  strength  of  the  solvent 
causing  extraordinary  variations  in  the  results. — Pharm.  Juor.  and 
Trans.,  Sept.  21,  1878. 
NOTE  on  NITRATE  of  SILVER  CONTAINING  GOLD. 
By  E.  B.  Suttleworth. 
It  does  not  appear  that  any  of  our  chemical  or  pharmaceutical 
authorities  give  gold  as  one  of  the  contaminations  of  nitrate  of  silver, 
yet  such  admixture  is  not  only  possible,  but  frequently  to  be  met  with 
in  common  grades  of  nitrate  which  have  been  prepared  directly  from 
solutions  of  the  metal.  All  commercial  refined  silver  contains  gold, 
though  perhaps  in  only  the  most  minute  quantity.  Of  nearly  three 
tons  which  have  been  dissolved  under  the  writer's  supervision,  none 
could  be  described  as  perfectly  pure  or  free  from  the  more  precious, 
metal.  English  refined  silver  generally  contains  more  than  American 
stamped  bars,  of  which  a  considerable  quantity  must  be  operated  on 
in  order  to  render  the  gold  appreciable. 
If  such  silver  be  dissolved  in  ordinary  nitric  acid  containing  traces  of 
hydrochloric  acid  both  metals  will  be  dissolved,  and,  as  long  as  the 
solution  is  acid  and  concentrated,  minute  quantities  of  both  chloride  of 
silver  and  chloride  of  gold  will  be  retained.  Crystals  deposited  from 
the  liquor  will  also  contain  traces  of  gold.  Such  crystals  have  a  faint 
purplish  tinge,  as  also  the  solution,  so  that  in  color  it  resembles  water 
containing  a  very  small  quantity  of  logwood  ink. 
I  am  not  prepared  to  say  in  what  particular  form  or  combination  the 
gold  exists  in  the  silver  salt,  nor  yet  to  state  the  effect  of  this  impurity 
on  the  photographic  film.  It  is,  however,  possible  that  some  of  the 
troubles  of  photographers — as,  for  instance,  that  technically  known  as 
fogging — might,  in  some  degree,  be  due  to  the  presence  of  this  con 
tamination. 
The  impure  salt  may  be  readily  prepared  for  experiment  by  adding 
to  a  concentrated  hot  solution  of  pure  nitrate  of  silver  a  few  drops  of 
solution  of  chloride  of  gold.      Flocks  of  chloride  of  silver  holding 
