Am.  Jour.  Pharm.  ) 
Nov.  1,  1872.  J 
Laboratory  Notes. 
495 
chloride  by  the  addition  of  a  large  volume  of  water,  excess  of  ammo- 
nia was  now  added,  the  precipitate  thrown  in  a  filter,  well  washed, 
and  the  acidified  filtrate  divided  into  two  equal  portions,  a  /9. 
Through  «,  H2S  was  passed  to  excess,  the  precipitate  so  formed 
collected,  washed  and  ignited.  The  residue  thus  obtained  is  a  mix- 
ture of  copper  sulphide,  oxide  and  sulphate.  To  remove  the  latter, 
it  was  again  carefully  ignited  with  ammonium  carbonate,  and  the  re- 
sulting mixture  of  copper  sulphide  and  oxide  weighed.  The  weight 
—  -0115  grains,  this  X  2  =  -0230  grains  in  quantity  taken  (3*2585 
grains)  and  -0230  gr.  =  -01836  grain  copper  — -563  per  cent,  copper 
in  sample  examined.  As  the  percentage  of  copper  in  copper  sulphide 
and  oxide  is  identical,  a  mixture  of  the  two  is  of  no  consequence  in 
estimating  the  amount  of  metallic  copper. 
The  portion  /?  of  the  filtrate  was  treated  in  a  similar  manner,  by 
passing  H2S  through,  but  the  resulting  precipitate  was  dissolved  in 
nitrohydrochloric  acid,  evaporated  to  dryness,  and  the  residue  dis- 
solved in  dilute  hydrochloric  acid.  From  this  solution  the  copper  was 
precipitated  as  metal  by  zinc  in  a  platinum  dish  in  the  usual  way.  The 
weight  of  metal  obtained  was  equal  to  -558  per  cent,  of  quantity  taken. 
The  me.an  of  the  two  experiments  ==  -563  +  -558  '2  —  -560  per 
cent. 
48*45  grains  of  impure  metal  were  then  fused  with  a  mixture  of 
2-5  grains  pure  K  Cy,  and  1*0  grain  S  for  fifteen  minutes.  The  fire 
was  then  removed,  and  after  a  few  moments,  to  allow  the  slag  to  sep- 
arate, the  crucible  being  gently  tapped  to  agglomerate  the  metal,  the 
latter  was  poured  out,  and  the  button  when  cold  weighed  : 
Weight  of  button  =■=  44*25  grains,  the  loss  was  therefore  4-20  grains 
=  8-6  per  cent. 
This  loss  is,  however,  much  too  great,  the  fact  being  that  I  did  not 
succeed  in  obtaining  the  whole  of  the  metal  in  the  button,  brilliant 
metallic  specks  being  visible  after  cooling,  disseminated  through  the 
slag.  A  second  fusion  of  the  latter  yielded  a  small  button,  but  on  ex- 
amination it  was  found  to  be  contaminated  with  particles  of  slag,  and 
consequently  gave  evidence  of  the  presence  of  copper. 
Subsequent  operations  have  proved  that  the  loss  should  never  ex- 
ceed five  per  cent, 
I  must  here  remark,  that  the  proportions  laid  down  by  Tamm  work 
well  if  pure  cyanide  be  used,  but  if  ordinary  commercial  fused  cyanide 
be  employed,  then  a  larger  proportion  is  necessary.    Practically,  1 
