94 
Phenol  as  a  Test  for  Nitrites,  etc. 
Am.  Jour,  Pharm. 
Feb.,  1889. 
with  phenol,  and  yellow  turning  brown  with  orcinol.  Potassium 
permanganate  gave  with  phenol  a  broad,  turbid,  light  reddish-brown 
band ;  and  with  hydrochloric  acid,  in  addition,  a  broad,  pale  yellow  upper 
band  with  a  narrow,  ruddy  lower  band,  changing  to  bright  vermilion ; 
with  orcinol,  it  gave  reddish  upper  and  dull  green  lower  band,  and  with 
hydrochloric  acid  in  addition  a  dull  orange  upper  and  emerald-green 
lower  band ;  in  presence  of  two  drops  of  sulphurous  acid,  no  reaction. 
Potassium  dichromate,  0*5  gram  per  litre  of  water,  with  or  without 
hydrochloric  acid,  gave  with  phenol  a  brown  band  soon  becoming 
lighter,  with  orcinol,  a  dull,  prismatic  band ;  in  presence  of  sulphurous 
acid  no  reaction ;  distinction  from  chlorates.  Hydrogen  peroxide,  3 
vols,  strength  diluted  with  20  vols,  of  water,  gave  with  phenol  a  red- 
dish upper,  and  dull  green  lower  band,  and  with  hydrochloric  acid  a 
very  faint,  purple  band,  changing  to  pink ;  with  orcinol,  a  sharp  red- 
dish band,  changing  to  dull  orange  above,  olive-green  below,  and  with 
hydrochloric  aqid  a  purple  upper,  weak  olive-green  lower  band ;  no  re- 
action in  presence  of  sulphurous  acid. 
The  above  reactions  refer  only  to  dilute  solutions  as  indicated  in  the 
paper ;  very  different  results  would  be  obtained  with  either  stronger 
reagents  or  stronger  solutions.  The  average  temperature  throughout 
these  experiments  was  about  26°. 
The  following  is  a  convenient  reagent  for  detecting  nitrites  or 
nitrates : — Dissolve  2'5  grams  of  orcinol  in  a  mixture  consisting  of  25 
cc.  of  2  per  cent,  copper  sulphate  solution,  1  cc.  of  pure  sulphuric  acid, 
and  25  cc.  of  pure  15  per  cent,  hydrochloric  acid,  and  filter;  2  drops 
of  this  are  added  to  0*5  cc.  of  the  solution  to  be  tested,  and  2  cc.  of 
sulphuric  acid  run  in.  If  the  reaction,  as  already  described  above, 
occurs  in  presence  of  sulphurous  acid,  nitrates  are  present. 
Guess'  Sulphanilic  Acid  Test  for  Nitrous  Acid. — The  author  takes 
5  cc.  of  nitrite  solution,  adds  1  drop  of  a  saturated  solution  of  sulpha- 
nilic acid  in  1  :  5  sulphuric  acid,  1  drop  of  phenol  or  thymol,  and 
after  10  minutes  mixes  well  with  1  cc.  of  ammonia.  Thymol  gives 
an  orange-yellow  not  so  defined  as  phenol.  The  limit  of  this  method, 
using  5  cc.  of  solution,  is  1  part  of  N203  in  10,000,000  of  water.  The 
author  suggests  the  use  of  the  method  in  the  reverse  order  as  a  test  for 
phenols.  Orcinol  gives  as  good  a  reaction  as  phenol,  but  becomes 
colored  of  itself  on  exposure  to  the  air  in  presence  of  alkali,  and  is 
therefore  untrustworthy. 
