RED  SANDAL  WOOD  AND  XANTHO  SANTALIC  ACID.  117 
it  is  evident  that  this  alkali  surpasses  all  the  other  agents  named, 
as  a  solvent  of  santalin. 
p  There  is  this,  however,  against  the  potash,  that  it  acts  as  a 
chemical  and  not  a  mechanical  solvent  in  this  case.  For,  not- 
withstanding it  acts  vigorously  upon  the  sandal  dust,  and  dis- 
solves the  far  greater  part,  if  not  all,  of  the  santalin,  the  coloring 
matter  in  it  is  of  a  dark  venous-blood  color ;  and  when  this  alka- 
line solution  is  applied  to  pale  wood,  such  as  the  tulip-tree 
(Liriodendron  tulipifera,)  it  retains  scarcely  the  remotest  tinge 
of  red,  but  assumes  a  snuff  color.  On  unsized  white  paper  it 
leaves  a  similar  stain.  In  both  cases,  according  to  this  view, 
acetic  acid  decomposes  the  compound  in  the  wood  and  the  paper, 
and  restores  the  red  color  of  santalin.  Paper  thus  prepared, 
with  the  potash  solution  of  santalin,  makes  a  tolerable  substi- 
tute for  blue  litmus  paper,  though  not  so  delicately  sensitive  as 
that. 
Santalin  precipitated  from  its  solution  in  sulphuric  acid,  is 
apparently  unchanged ;  concentrated  sulphuric  acid  dissolves 
santalin  without  exerting  any  obvious  chemical  action  upon  it. 
Nitric  acid,  on  the  other  hand,  changes  the  color  to  a  sienna 
hue;  and  on  the  sandal  wood  dust  its  chemical  agency  is  very 
manifest,  being  attended  with  a  prompt  and  long  continued  ef- 
fervescence, extending  even  to  many  hours,  and  resulting  in  a 
combination  or  compound  of  a  yellowish  brown  color,  which  is 
so  unalterable  that  neither  concentrated  sulphuric  acid  affects  it, 
(when  precipitated  by  water  and  washed)  nor  concentrated  am- 
monia, nor  potash,  nor  any  other  chemical  agent  that  I  sub- 
jected it  to;  except  that  the  alkalies  very  readily  dissolve  it. 
From  some  hasty  experiments,  I  infer  that  this  compound  acts 
the  part  of  an  acid  toward  the  alkalies,  and  at  least  some  metals. 
I  will  call  it,  conditionally,  and  to  avoid  circumlocution,  Xantho- 
santalic  acid.  Proceeding  with  this  nomenclature,  it  appears  as 
above  that  the  xanthosantalate  of  ammonia  and  of  potash  are 
soluble  in  water. 
To  the  solution  of  xanthosantalate  of  potash,  I  added  solution 
of  sulphate  of  copper.  The  precipitate  obtained  was  w.ashed, 
and  treated  with  acetic  acid  so  long  as  any  cupreous  compound 
was  formed  with  this  acid.  The  tar-colored  residue  on  the  filter 
was  then  washed,  and  hydrochloric  acid  added  to  it  on  the  filter. 
A  tar-colored  solution  passed  through  as  a  filtrate,  holding  no 
