PRODUCTION  OF  ALIZARIN  FROM  NAPHTHALIN.  559 
Naphthalin  is  produced  in  large  quantities  in  the  manufacture  of 
gas,  and  has  hitherto  been  nothing  more  than  a  waste  product ; 
its  conversion,  therefore  into  so  valuable  an  agent  as  alizarin,  will 
form  an  important  addition  to  the  list  of  discoveries  which  have 
recently  added  so  much  to  the  resources  of  the  dyer. 
That  some  connection  exists  between  the  alizarin  and  the  naph- 
thalic  series  of  bodies,  has  been  recognized  bj  chemists,  and  the 
probability  of  the  conversion,  has  we  believe,  tempted  more  than 
one  experimenter. 
M.  Roussin's  process  consists  in  making  a  mixture  of  binitro- 
naphthalin  and  concentrated  sulphuric  acid  in  a  large  porcelain 
dish  heated  by  a  sand  bath.  As  the  temperature  rises,  the  bini- 
tro-naphthalin  dissolves  completely  in  the  acid,  forming  an  amber 
colored  solution.  When  the  mixture  is  at  200°  Cent,  some  finely 
granulated  zinc  is  added.  In  a  few  instants  an  evolution  of  sul- 
phurous acid  takes  place,  and  in  half  an  hour  the  operation  is 
completed.  If  a  drop  or  two  of  the  acid  liquid  be  now  thrown 
into  cold  water,  a  deep  red  violet  color  is  developed,  owing  to  the 
formation  of  alizarin.  It  is  important  in  operating  upon  any 
large  quantity  of  materials,  to  add  the  zinc  in  small  successive 
portions,  and  to  take  care  that  the  temperature  of  the  acid  liquid 
does  not  exceed  the  point  indicated,  as  otherwise  the  reaction 
becomes  excessively  violent,  and  the  proportion  of  alizarin  is  di- 
minished. 
The  liquid  resulting  from  the  above  reaction,  is  diluted  with 
eight  or  ten  times  its  volume  of  water,  boiled  for  a  few  minutes, 
and  then  thrown  on  a  filter.  On  cooling,  the  alizarin  is  deposited 
in  the  form  of  a  red  jelly,  which,  when  examined  under  the  micro- 
scope, is  seen  to  consist  of  distinct  needle-like  crystals.  The 
mother  liquor  has  a  deep  red  color,  and  contains  a  considerable 
quantity  of  alizarin  in  solution.  When  diluted  with  water  and 
properly  neutralized,  it  can  be  used  directly  for  dyeing  purposes. 
It  contains  a  large  amount  of  sulphate  of  ammonia  in  solution. 
In  this  process  the  zinc  may  be  replaced  by  tin,  iron,  sulphur, 
carbon,  and  other  bodies  of  a  like  nature. 
We  may  represent  the  reaction  which  takes  place  by  abstract- 
ing from  the  binitro-naphthalin  (C2oH^(N20g)  ),  two  atoms  of  ni- 
trogen and  two  of  oxygen,  when  the  formula  of  alizarin  (G^q 
Og)  is  obtained.    The  N2  O2  so  removed,  by  taking  eight  atoms  of 
