216   Tablets  Contains  Salol  and  Quinine  Sulphate.  { Am-  ^°au£  f££m- 
Add  petroleum  ether2  to  the  mixture  in  the  beaker,  using  10 
mil  portions  (making  about  five  or  six  extractions),  decant  through 
a  dry  filter  paper,  collecting  the  filtrate  in  a  weighed  glass  dish. 
Evaporate  the  solvent  on  a  water  bath,  allowing  a  current  of  air 
from  an  electric  fan  to  assist  the  evaporation.  When  the  solvent  is 
nearly  volatilized  remove  the  dish  from  the  water  bath  and  allow 
the  remainder  of  the  solvent  to  evaporate  spontaneously,  using  the 
current  of  air  from  the  fan.  Weigh  residue  immediately  upon  the 
absence  of  petroleum  ether  odor.3  If  the  determination  is  made  as 
above  directed  the  loss  due  to  the  volatilization  of  the  salol  is 
negligible. 
The  residue,  if  salol,  will  give  the  following  tests : 
The  distinctive  odor  of  salol. 
Melting  point  41  to  43 0  C. 
Cone,  nitric  acid — colorless. 
Froede's  reagent — deep  purple,  gradually  to  an  olive  green. 
Formaldehyde  sulphuric  acid — pink  to  a  very  deep  pinkish  red. 
Selenous  sulphuric  acid — colorless  to  a  faint  yellow. 
Ferric  chloride — no  change  in  color. 
Salol  is  saponified  by  sodium  hydroxide,  and  if  an  excess  of 
hydrochloric  acid  is  then  added,  salicylic  acid  will  be  precipitated 
(if  sufficient  salol  is  taken)  and  phenol  liberated  which  can  be  rec- 
ognized by  its  distinctive  odor.  Both  of  these  liberated  products 
can  be  removed  by  ethyl  ether,  and  tested  with  ferric  chloride,  which 
gives  a  violet  coloration. 
Quinine  Sulphate.4 — The  residue  in  the  beaker  is  repeatedly  ex- 
tracted with  10  mil  portions  of  a  mixture  of  chloroform  and  abso- 
lute alcohol,5  making  about  six  to  eight  extractions.  Decant  through 
the  filter  paper  used  in  the  determination  of  salol,  and  collect  filtrate 
in  a  weighed  glass  dish,  evaporate  to  dryness  and  heat  at  no°  C. 
until  a  constant  weight  is  obtained. 
2  Merck's  benzin  (petroleum  ether)  reagent  is  used.  The  quinine  sulphate 
is  practically  insoluble  in  benzin. 
3  If  the  dish  containing  the  salol  is  allowed  to  remain  on  the  steam  bath 
for  one  half  hour,  a  correction  of  about  5  per  cent,  must  be  made,  due  to  loss 
of  salol  by  volatilization.  This  factor,  however,  must  be  determined  by  run- 
ning a  known  sample  of  salol  in  parallel  with  the  unknown  under  the  same 
conditions.  It  is  advisable  to  determine  the  salol  roughly  at  first,  and  then 
use  this  figure  as  an  index  of  the  amount  of  authentic  salol  required  for  the 
control  determination. 
