Am.  Jour.  Pharin.  \ 
March,  1892.  / 
Alpha-  and  Beta-Naphthol. 
161 
A  READY  METHOD   OF  DISTINGUISHING  BETWEEN 
ALPHA-  AND  BETA-NAPHTHOL. 
By  F.  W.  Richardson,  F.C.S.,  etc. 
Having  occasion  to  test  the  contents  of  two  bottles  to  ascertain 
which  was  alpha-  and  which  beta-naphthol,  I  applied  the  methods 
of  N.  Yvon,  described  in  the  Chemical  News  (vol.  lxiv.,  p.  321), 
but  obtained  very  unsatisfactory  results  ;  indeed  process  (2),  as 
might  be  expected,  gave  no  result  whatever. 
Remembering  that  the  difference  between  the  azo-dyes  "  Orange 
I"  and  "Orange  II"  is  entirely  due  to  the  fact  that  while  for  the 
preparation  of  the  former  dye  a-naphthol  is  used,  /3-naphthol  is 
required  for  the  latter,  I  worked  out  the  following  process : 
Dissolve  about  5  cgm.  of  sulphanilic  acid  in  a  little  water  con- 
taining about  5  cc.  of  normal  soda  ;  add  5  cc.  of  normal  sulphuric 
acid,  and  mix  the  solution  with  2  cgm.  of  sodium  nitrite  dissolved 
in  a  few  drops  of  water. 
Dissolve  a  little  (about  4  cgm.)  of  the  naphthol  by  the  aid  of  a 
few  drops  (0  5  cc.)  of  normal  soda,  and  into  this  solution  pour  the 
diazotized  sulphanilic  acid.  With  a-naphthol  the  liquid  becomes 
dark  blood-red ;  with  /3-naphthol  only  a  reddish-yellow  color  is 
produced  ;  this  difference  is  most  marked  when  the  dyes  are  salted 
out. 
The  a-naphthol  dye  becomes  dark  brown  with  dilute  sulphuric 
acid,  while  the  /9-naphthol  compound  is  quite  unchanged  :  this  last 
reaction  is  very  distinctive. 
The  equations  representing  the  changes  which  take  place  are  as 
follows  : 
C6H4.H.SOs.NH2  -f  2HCI  +  NaN02  =  NaCl  4-  2H20  -f 
Sulphanilic  acid. 
+  C6H4H.S03.N  =  N  —  CI. 
Diazobenzol-sulphonic  acid 
chloride. 
C6H4.H.S03.N  —  N  —  CI  +  2NaHO  +  C10H7(HO)  =  NaCl  + 
Naphthol. 
N  =  N  -  C10H6(HO)  (a  or  /?) 
_J_  2HX>  +  CH/  Orange  I  or  Orange  II. 
2    ^    6  4\NaS03. 
Sodiumnaphtholdiazobeneene-sulphonate. 
—  Chem.  News,  Jan.  8,  1892,  p.  i8« 
