DETERMINATION  OP  GRAPE-SUGAR,  ETC. 
81 
of  lead.  No  doubt  can  therefore  exist  about  the  identity  of 
Pelouze's  acid  and  my  product.  The  equivalents  of  gallic  acid 
are  divided  exactly  into  one  equiv.  of  gallhumic,  two  equiv.  of 
carbonic  acid,  and  three  equiv.  of  water  : 
f  C12H303 
C14H6O10==« 
j  H303 
I  CuIP010 
This  origin  of  gallhumic  acid  forms  another  and  interesting  ar- 
gument, that  pyro-acids  can  be  obtained  otherwise  than  by  the 
action  of  heat. 
If  some  powdered  "  red  precipitate  "  is  added  to  a  solution  of 
gallic  acid  and  heated  over  a  spirit  lamp,  it  is  immediately  re- 
duced ;  gallic  acid  precipitates  suboxyd  of  copper  (red  oxyd)  in 
a  solution  of  sulphate  of  copper  ;  this  reaction  appears  with  the 
greatest  facility  if  the  solutions  are  heated  together.  It  also  re- 
duces a  cold  solution  of  neutral  chromate  of  potassa,  producing 
the  green  sesquioxyd.  The  gallic  acid  is  in  each  of  these  cases 
transformed  into  gallhumic  acid.  The  action  of  these  substances 
on  gallic  acid  and  the  formation  of  the  new  product,  is  explained 
by  assuming  gallhumic  acid  to  be  only  an  intermediate  product, 
the  final  result  being  carbonic  acid  and  water. — Am.  Jour,  of 
ScL  and  Arts,  Nov.  1859. 
ON  THE  DETERMINATION  OF  GRAPE-SUGAR,  CANE-SUGAR  AND 
DEXTRINE  IN  THEIR  MIXTURES. 
By  J.  G.  Gentele. 
The  analysis  of  a  mixture  containing  grape-sugar,  cane-sugar, 
and  dextrine,  or  only  two  of  these  substances,  is  founded  upon 
the  following  facts  : — 
1.  A  mixture  of  1  part  of  ferridcyanide  of  postassium  (the 
red  prussiate)  with,  half  a  part  of  hydrate  of  potash,  dissolved 
in  water,  has  no  action  upon  a  pure  solution  of  cane-sugar, 
either  at  ordinary  temperatures  or  when  heated  to  boiling.  An 
extraordinarily  small  quantity  of  this  reagent  gives  the  fluid  a 
strong  yellow  color,  and  this  color  is  persistent. 
2.  The  same  reagent  applied  to  a  solution  of  grape-sugar  loses 
6 
