ACTION  OF  GLUCOSE  ON  SALTS  OF  COPPER  IN  ACETATES.  141 
supposed  that  the  acetate  of  copper  would  remain  in  the  mix- 
ture when  boiled  ;  but  it  is  found  by  experiment,  that  at  the 
temperature  of  ebullition  the  mixture  is  composed  of  bichloride 
of  copper  and  acetate  of  soda ;  so  that  heat  causes  a  reaction 
the  reverse  of  that  which  takes  place  at  ordinary  temperatures. 
To  see  this  phenomenon  clearly,  certain  precautions  must  be 
taken.  When  bichloride  of  copper  in  excess  is  mixed  with  ace- 
tate of  soda,  a  precipitate  is  formed,  especially  by  boiling,  which 
prevents  the  action  of  glucose  on  the  mixture.  The  same  pre- 
cipitate is  formed  by  mixing  acetate  of  potash,  magnesia,  manga- 
nese, zinc,  cadmium,  strontian,  cobalt,  or  nickel  with  the  bichlo- 
ride of  copper.  This  precipitate  is  also  produced  by  boiling  ace- 
tate of  copper  with  an  excess  of  bichloride  of  copper,  and  also 
when  chloride  of  sodium  is  added  to  acetate  of  copper. 
If  an  excess  of  a  very  concentrated  solution  of  acetate  of 
soda  be  poured  into  a  solution  of  bichloride  of  copper,  and  glu- 
cose be  added  to  the  mixture,  protochloride  of  copper  is  formed 
on  boiling,  and  its  presence  is  more  or  less  distinct  according  to 
the  quantity  of  the  acetate.  If  this  be  not  in  very  great  excess, 
the  protochloride  is  seen  to  precipitate,  leaving  a  colorless  su- 
pernatant fluid.  If  the  acetate  of  soda  be  in  very  great  excess, 
the  protochloride  of  copper  is  decomposed  by  it  as  fast  as  it  is 
formed,  and  the  final  result  is  protoxide  of  copper. 
Acetate  of  Gopper. — When  acetate  of  copper  is  boiled  with 
glucose,  whatever  may  be  the  excess  of  sugar  and  the  period 
during  which  the  mixture  is  boiled,  the  whole  of  the  copper  is 
never  precipitated,  some  of  it  always  remaining  in  the  liquid. 
To  effect  the  complete  reduction  of  acetate  of  copper,  it  is  suffi- 
cient to  mix  a  great  excess  of  acetate  of  soda  or  potash  with  this 
salt.  This  explains  why  the  whole  of  the  copper  is  precipitated 
when  a  great  excess  of  acetate  of  soda  or  potash  is  mixed  with 
the  sulphate  or  nitrate  of  copper  before  boiling  it  with  the  glu- 
cose. 
Sesquisulphate  and  Sesquinitrate  of  Iron. — Acetate  of  cop- 
per, mixed  with  either  of  these  salts,  loses  the  faculty  of  being 
reduced  by  glucose.  This  character,  and  the  peculiar  color  of 
acetate  of  iron  which  makes  its  appearance  at  the  moment  of 
mixture,  prove  that  the  acetate  of  copper  is  decomposed  by  the 
iron-salts. 
