140    ACTION  OF  GLUCOSE  ON  SALTS  OF  COPPER  IN  ACETATES. 
If,  before  pulverizing,  it  shows  partly  a  darker  or  even  black 
color,  the  reduction  has  not  been  complete. 
Another  probably  more  recommendable  mode  for  preparing 
the  iron,  is  the  reduction  of  the  oxalate  of  the  protoxide  iron  by 
hydrogen.  This  salt,  remarkable  for  its  fine  lemon-color,  may, 
as  is  well  known,  be  obtained  by  precipitation  of  concentrated 
solution  of  sulphate  of  iron  with  oxalic  acid.  The  dry  salt  is 
so  easily  and  at  so  low  a  heat  reduced  by  the  hydrogen,  that  a 
glass  tube  will  answer  excellently  for  the  operation  ;  towards 
the  end,  however,  the  tube  must  be  heated  to  dull  redness,  to 
prevent  the  iron  powder  from  becoming  pyrophoric,  and  after- 
wards the  apparatus  must  be  allowed  to  cool,  as  the  iron,  if  only 
little  warm,  will  burn  in  coming  in  contact  with  the  air.  (Anna- 
len  d.  Chem.  and  Pharm.,  1855,  April  125,  August  192.) 
ON  THE  ACTION  OF  GLUCOSE  ON  THE  SALTS  OF  COPPER  IN 
THE  PRESENCE  OF  ACETATES. 
By  M.  Alvaro  Reynoso. 
Sulphate  of  Copper  It  is  well  known  that  when  sulphate  of 
copper  is  boiled  for  a  long  time  with  glucose,  it  is  decomposed, 
and  metallic  copper  is  precipitated.  If  the  sulphate  of  copper 
be  mixed  with  acetate  of  soda,  potash,  lime,  magnesia,  zinc,  co- 
balt, nickel  or  manganese,  and  then  boiled  with  glucose,  a  reduc- 
tion is  immediately  produced,  and  protoxide  of  copper  is  precipi- 
tated. This  reaction  shows  that  sulphate  of  copper  is  decom- 
posed by  contact  with  these  acetates,  forming  acetate  of  copper, 
which  is  reduced  by  the  glucose. 
Nitrate  of  Copper. — This  salt,  mixed  with  any  of  the  above 
acetates,  or  with  acetate  of  cadmium,  strontian  or  lead,  and 
boiled  with  glucose,  furnishes  a  precipitate  of  protoxide  of  cop- 
per. Although  this  precipitate  is  also  produced  by  boiling  ni- 
trate of  copper  alone  with  glucose,  there  is  no  reason  to  doubt 
the  formation  by  double  decomposition  of  acetate  of  copper,  for 
in  the  latter  case  the  reaction  takes  place  at  the  moment  of 
ebullition,  whilst  with  the  nitrate  alone  it  requires  long  boiling. 
Bichloride  of  Copper  When  concentrated  solutions  of  bi- 
chloride of  copper  and  acetate  of  soda  are  mixed,  the  acetate 
of  copper  soon  crystallizes.    At  first  sight  it  might  therefore  be 
