CONTRIBUTIONS  TO  THE  HISTORY  OF  NAPHTHALINE.  237 
M.  Roussin,  who  is  chiefly  occupied  with  the  reds.  We  soon 
found  that  binitronaphthaline,  heated  with  sulphuric  acid  only, 
was  best  suited  to  our  purpose.  In  his  last  communication  to 
the  Institute  (Comptes  Hendus,  vol.  lii.  p.  1033,)  M.  Roussin  says: 
— "By  making  concentrated  sulphuric  acid  react  on  binitro- 
naphthaline, no  reaction  takes  place.  The  binitronaphthaline 
is  completely  dissolved,  when  the  mixture  is  heated  to  250°, 
and  the  liquid  takes  hardly  an  amber  color.  After  boiling 
for  a  long  time,  the  concentrated  sulphuric  acid  began  to  react 
on  this  substance."  Binitronaphthaline  resists  the  action  of  sul- 
phuric acid  at  a  very  high  temperature,  however,  at  about  300°; 
the  color  of  the  solution,  at  first  slightly  yellow,  deepens  more 
and  more,  becomes  cherry-red,  and  finally  brownish-red,  begin- 
ning at  the  same  time  to  disengage  a  small  quantity  of  sulphu- 
rous acid.  The  progress  of  the  operation  is  easily  followed  by 
taking  up  occasionally  a  drop  of  the  liquid  with  a  rod,  and  drop- 
ping it  into  a  glass  of  water.  Thus  at  first  a  white  milky  pre- 
cipitate is  obtained,  then  a  light  violet ;  and,  finally,  when  the 
color  is  completely  developed,  a  dark  violet. 
The  substance  is  then  taken  from  the  fire,  and  left  to  cool, 
when  it  is  poured  into  a  proper  quantity  of  water  and  boiled. 
The  liquid,  filtered  whilst  hot,  is  of  a  deep  red  color,  and  de- 
posits part  of  the  coloring  matter  in  a  flaky  state.  Alkalies 
change  it  to  a  violet  red ;  and  even  when  cold,  silk  was  easily 
dyed  violet  by  it.  After  being  properly  saturated  with  alkalies, 
and  finally  with  a  little  chalk,  it  dyed  mordanted  cotton  tissues 
with  different  shades,  varying  from  lilac  to  black.  The  lakes 
with  alum,  tin,  and  lead  for  a  base,  are  violet ;  those  with  iron 
for  a  base   were  olive,  and  sometimes  reached  to  black. 
In  fact,  this  solution  does  not  seem  to  alter  even  during  any 
length  of  time,  in  presence  of  sulphuric  acid ;  though,  when  in 
contact  with  air  and  excess  of  ammonia,  it  changes  to  brown  in 
a  few  hours,  depositing  a  black  powder,  which  becomes  blue  when 
dissolved  in  alcohol,  and  red  in  acids. 
The  black  mass  proceeding  from  the  precipitation  of  the  sul- 
phuric solution  by  water,  contains  a  large  quantity  of  coloring 
matter,  which  we  were  able  to  separate  by  means  of  M.  Payen's 
digesting  apparatus.  This  coloring  matter  has  a  beautiful  gold 
reflection,  is  very  soluble  in  alcohol  and  pyroligneous  acid ;  but 
