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ON  VEGETABLE  BRONZE-COLORS. 
remains  to  be  ascertained  what  temperature  is  the  most  proper 
for  the  conversion  of  the  whole  of  the  perchloride  into  calomel. 
— Chem.  Gfaz.,  July,  1854,  from  Ann.  der  Ohem.  und  Pharm., 
xc.  p.  124. 
ON  VEGETABLE  BRONZE-COLORS  FROM  BRAZIL-WOOD  AND 
LOGWOOD. 
By  L.  Denzer. 
When  alum  is  dissolved  by  heat  in  a  decoction  of  Brazil-wood, 
which  has  been  cleared  by  standing  for  several  days,  a  precipitate 
is  produced  on  the  cooling  of  the  solution,  which  increases  in  pro- 
portion to  the  length  of  time  the  fluid  is  left  standing,  and  at 
last  contains  nearly  all  the  coloring  matter.  If  this  precipitate 
be  washed  once  with  water,  and  spread  in  a  tolerably  thick  coat- 
ing upon  paper,  it  dries  with  a  beautiful  shining  gold  color,  with 
a  slight  tendency  to  green,  very  like  the  dried  wing-cases  of  the 
common  cantharides.  If  the  precipitate  be  made  into  a  paste, 
mixed  with  a  little  size  and  glaze  (prepared  by  dissolving  wax  in 
soap),  and  then  laid  on  the  paper  by  means  of  a  brush,  it  may  be 
polished  with  an  agate  or  glass  ball,  and  then  acquires  a  beautiful 
yellow  metallic  lustre,  exactly  like  bronze.  It  is,  however,  ne- 
cessary for  this  purpose,  that  the  paper  should  be  so  thickly 
coated  with  the  color  as  to  render  it  quite  opake. 
A  coloring  matter  obtained  from  logwood  has  exactly  the  same 
properties,  but  its  preparation  is  somewhat  different,  and  the  me- 
tallic lustre  has  more  of  a  coppery  tint,  the  former  rather  re- 
sembling brass. 
If  a  freshly  prepared  concentrated  decoction  of  logwood  be 
heated  in  a  copper  kettle,  and  then  mixed  with  chloride  of  tin, 
an  abundant  dark  brown  precipitate  is  obtained,  which  is  to  be 
collected  without  washing.  The  precipitate,  when  employed  like 
the  preceding  one,  communicates  a  copper-bronze  color  to  paper. 
A  different  shade  is  obtained  when  the  hot  decoction  of  logwood 
is  first  mixed  with  a  little  alum,  and  afterwards  with  a  still 
smaller  quantity  of  bichromate  of  potash ;  this  precipitate  is 
darker,  and  its  lustre,  when  laid  on  paper,  has  more  of  a  yellow- 
ish tinge,  so  that  it  forms  an  intermediate  shade  between  the 
other  two  colors. 
