254     PREPARATION  OF  ARTIFICAL  COLORING  MATTERS,  ETC. 
heated  on  a  water-bath  to  100°,  and  7  parts  of  mercuric  nitrate, 
dry  and  in  powder,  are  added  by  degrees.  The  mixture  is 
is  maintained  at  the  temperature  of  100^  for  eight  or  nine 
hours,  in  which  time  the  mass  will  have  become  of  a  magnifi- 
cent violet-red  color.  On  cooling  it  forms  a  thick  paste.  The 
greater  part  of  the  reduced  mercury  is  found  at  the  bottom  of 
the  vessel.  To  employ  the  azaleine  then  produced  as  a  dye  or 
for  printing,  it  is  only  necessary  to  treat  the  pasty  mass  with 
boiling  water,  a  mixture  of  water  and  alcohol,  acetic  acid,  or 
any  other  solvent,  and  make  use  of  the  solution. 
The  advantage  of  the  last  process  consists  in  the  moderate 
heat  required,  a  high  temperature  seeming  to  cause  the  forma- 
tion of  tarry  matters. 
M.  Albert  Schlumberger  has  also  described  (Bulletin  de  la 
Societe  Indmtrielle  de  Mulhouse,  March  1860,  p.  170)  a  process 
for  converting  aniline  into  red  coloring  matter  by  means 
of  the  neutral  nitrate  of  mercury.  He  takes  100  parts  of 
anhydrous  aniline,  and  60  parts  of  the  nitrate  of  mercury,  and 
heats  the  mixture  to  boiling.  The  mass  slowly  changes  color, 
at  first  becoming  brown,  but  in  time  the  whole  is  transformed 
into  a  beautiful  red  liquid.  The  operation  is  finished  when  the 
boiling  materials  are  observed  to  swell  up  and  disengage  yellow- 
ish vapors.  The  mass  so  obtained  is  washed  with  two  or  three 
times  its  volume  of  boiling  water,  to  remove  the  oils  which  are 
not  completely  metamorphosed,  and  then  boiled  two  or  three 
times  with  water  to  extract  the  coloring  matter. 
In  this  process,  as  well  as  in  the  preceding,  the  whole  of  the 
mercury  is  recovered. 
In  May,  1860,  MM.  Girard  and  Delaire  obtained  a  patent 
for  the  use  of  arsenic  acid  in  the  preparation  of  a  red  color- 
ing matter  from  aniline.  They  introduce  into  a  distillatory 
apparatus  12  parts  of  dry  arsenic  acid  and  12  parts  of  water. 
When  the  hydration  of  the  arsenic  acid  is  complete,  they  add 
10  parts  of  aniline,  and  shake  the  whole  well  together.  The 
mass  becomes  homogeneous,  pasty,  and  almost  solid.  A  gentle 
heat  is  then  applied,  so  as  to  raise  the  temperature  of  the  mix- 
ture gradually.  The  mass  now  becomes  liquid.  When  the 
operation  is  properly  conducted,  only  water  and  a  very  small 
quantity  of  aniline  distil.     At  120^  a  great  part  of  the  aniline 
