BUTTER  AS  A  REAGENT  FOR  COPFER,  ETC. 
371 
placed  thorn  separately  in  three  different  vessels.  He  then  filled 
one  of  these  Avith  water  taken  from  a  wooden  hydrant  placed  in 
his  yard  at  some  distance  from  that  of  copper;  the  second  ves- 
sel was  filled  with  water  from  the  .very  well  that  supplied  the 
copper  pipe,  but,  from  the  outside  of  that  pipe  ;  and  the  third 
vessel  contained  water  that  had  passed  through  the  copper  pipe 
itself. 
The  butter  deposited  in  the  water  of  the  third  vessel  was  the 
only  one  which,  after  two  days  immersion,  became  covered  with 
a  bluish  green  color,  exhibiting  the  aspect  of  an  hydrate  of  deu- 
toxide  of  copper. 
This  piece  of  colored  butter  was  handed  to  me  by  the  owner, 
with  a  request  to  experiment  chemically  upon  it,  so  as  to  ascer- 
tain the  true  nature  of  this  coloration. 
A  solution  of  hydro  sulphuric  acid  applied  to  the  butter,  pro- 
duced at  once  a  blackish  dirty  spot ;  and  the  ferro-hydrocyanate 
of  potassa  gave  a  crimson  spot:  the  latter  grew  darker  by  de- 
grees. These  characteristic  aspects  left  no  doubt  of  the  pres- 
ence of  copper. 
Desirous  of  experimenting  upon  the  very  water  that  had  im- 
parted such  a  color  to  the  butter,  and  also  of  determining  what 
proportion  of  copper  it  might  contain,  I  requested  the  owner  to 
Bend  me  a  certain  quantity  of  that  water,  especially  that  which 
would  be  the  first  drawn  in  the  morning.  He  sent  me  about 
three  gallons  of  it,  one  quart  of  which  was  tried  by  means  of  the 
above  mentioned  reactives,  and  some  well-known  others,  but  with- 
out any  result. 
The  remaining  eleven  quarts  were  reduced  by  evaporation 
to  a  tumbler  full.  Having  filtered  that  remnant,  I  tried  the 
limpid  liquor:  no  result.  I  next  poured  on  the  filter — now 
coated  with  a  calcareous  deposit — a  few  drops  of  a  reagent : 
again  without  result.  I  dissolved  this  deposit  in  nitric 
acid,  and  then  neutralized  the  solution ;  but  that  was  as  unsuc- 
cessful as  the  other  trials. 
Now,  what  conclusions  can  be  drawn  from  the  above  ?  Simply 
this :  That  butter  may  fix  and  reveal  molecules  of  copper,  so 
very  minute,  that  they  will  evade  the  most  sensitive  reagents 
known.    Another  remark  is,  that  none  of  the  persons  who  had 
