DYE  PIGMENT  FROM  QUERCITRON  BARK.  353 
nishes  an  excellent  writing  and  copying  ink,  whilst  even  with  1 
part  of  cake-ink  and  10  to  15  parts  of  water,  beautiful  writing- 
inks  are  obtained. — Chem.  Cf-az.,  March,  1857 ,  from  Mittheil. 
des  Gfeioerbevereins  fur  das  Konifir.  Hannover. 
PREPARATION  OF  DYE  PIGMENT  FROM  QUERCITRON  BARK 
Quercitron  bark  contains  a  considerable  amount  of  tannin, 
which  in  the  dyeing  enters  into  combination  with  the  mordants, 
and  thereby  injures  the  brightness  of  the  colors.  When  the 
bark  is  treated  with  sulphuric  acid  the  tannin  is  separated,  and 
the  colors  then  obtained  are  much  brighter  and  richer. 
M.  Rigaud's  observation  that  quercitron  is  converted  by  the 
action  of  sulphuric  acid  into  quercitin  was  first  practically  ap- 
plied by  M.  Leeshing,  who  subjected  quercitron  bark  to  the  action 
of  sulphuric  acid. 
Hr.  SchafFer  recommends  the  following  proportions  : — 
The  bark  is  to  be  boiled  for  two  hours  with  the  acid,  then 
washed  five  or  six  times  by  decantation,  and  the  residue  pressed. 
This  product,  when  dry,  is  equal  to  three  times  as  much  of  the 
bark. 
Hr.  Schlumberger  recommends  : — 
Quercitron  bark   100  parts 
Water   300  « 
Sulp-huric  acid   15  " 
He  finds  that  the  conversion  of  tannin  into  gallic  acid  requires  a 
^emperature  of  212°  F.;  that  neither  lime  nor  potash  is  extract- 
ed from  the  bark  by  this  treatment.  When  the  product  is  mixed 
with  cold  water,  and  then  with  pernitrate  of  iron,  the  reaction  of 
tannin  is  very  slight,  but  an  alcoholic  decoction  gives  a  precipi- 
tate with  gelatine.  He  also  finds  that  when  quercitron  bark,  or 
the  product  obtained  by  the  action  of  sulphuric  acid  upon  the 
bark,  is  mixed  with  tannin,  the  colors  obtained  are  somewhat 
darker,  but  more  muddy  ;  the  addition  of  gelatine  counteracts 
this  effect  completely.    When  gallic  acid  was  added  in  the  dye- 
Quercitron  bark 
Water  
Sulphuric  acid  . 
100  parts 
280  « 
26  « 
23 
