AmFe°b"imarm'}     Phenol  as  a  Test  for  Nitrites,  etc.  93 
sulphuric  acid  due  to  nitrites  is  first  obtained ;  and  then,  after  treatment 
with  sulphurous  acid,  the  chlorate  may  be  detected  by  the  blue  color 
with  orcinol  and  sulphuric  acid.  The  results  show  that  chlorate  can  be 
detected  when  mixed  with  a  considerable  excess  of  nit  rite  after  the  latter 
has  been  destroyed  with  sulphurous  acid,  but  nitrites  cannot  be  detected 
by  this  method  if  the  chlorate  is  greatly  in  excess.  With  mixtures  of 
chlorates  and  nitrates,  the  former  cannot  be  detected  if  the  latter  are  in 
considerable  excess  ;  but,  on  the  other  hand,  a  small  quantity  of  nitrate 
can  be  detected  in  the  presence  of  a  large  quantity  of  chlorate,  since  by 
allowing  the  sulphurous  acid  to  act  for  about  15  minutes  the  chlorate 
is  completely  destroyed,  whilst  the  nitrate  remains  and  gives  its  color 
reaction  in  the  usual  manner ;  when,  however,  the  chlorate  is  not  in  great 
excess  the  nitrate  may  even  be  detected  with  hydrochloric  acid,  phenol, 
and  sulphuric  acid,  without  previously  destroying  the  chlorate.  When 
all  three  are  present  in  the  same  solution,  they  can  be  tested  by  these 
reactions  only  when  the  proportions  indicated  above  are  not  exceeded ; 
for  instance,  a  mixture  of  equal  volumes  of  10,000  iN~203, 10,000  N205, 
and  10,000  C1205  would  give  the  red  band  with  phenol  and  sulphuric 
acid  for  nitrites ;  a  blue  band  with  1  drop  of  sulphurous  acid  and  1 
drop  of  orcinol  for  chlorates ;  and  by  treatment  with  2  drops  of  sul- 
phurous acid  and  1  drop  of  hydrochloric  acid,  allowing  to  remain  15 
minutes,  copper  sulphate  and  orcinol  would  give  the  orange  bands  due 
to  nitrate. 
The  presence  of  iodides,  bromides,  and  even  chlorides  in  large 
quantities  would  prevent  the  detection  of  nitrites,  nitrates,  or  chlorates 
by  this  method,  if  these  are  present,  therefore,  the  solution  must  be 
precipitated  with  silver  sulphate.  Thymol  and  a-naphthol  do  not  give 
distinct  and  characteristic  reactions  for  these  salts  under  the  conditions 
given  in  the  paper ;  but  the  following  test  is  recommended  by 
the  author  for  nitrite  in  very  dilute  solutions  :  two  or  three  drops 
of  the  alcoholic  a-naphthol  and  one  or  two  drops  of  1  :  1  sulphuric 
acid  added  to  10  cc.  of  1  in  1,000,000  nitrite  solution,  gives  in  a 
few  minutes  a  pale,  greenish-  yellow  color ;  with  much  stronger 
solutions,  a  precipitate  separates,  and  the  color  of  the  liquid  ap- 
proaches orange. 
For  the  sake  of  comparison,  the  following  substances  were  tested  with 
sulphuric  acid  and  1  drop  of  phenol  or  1  drop  of  orcinol  to  0*5  cc.  of 
the  solution  : — Potassium  ferricyanide  in  strong  solution  gave  a  brown 
band  with  sulphuric  acid  alone,  in  weak  solutions  it  gave  a  brown  band 
