PURITY  OF  SULPHATE  OF  QUININE   OF  COMMERCE.  48 
of  quinine,  quinidine,  or  cinchonidine,  yet  it  requires  consider- 
able experience  with  an  expensive  polarizing  microscope,  with 
great  consumption  of  time,  to  give  good  results,  when  only  a 
minute  quantity  is  operated  on. 
The  chlorine  and  ammonia  test  of  Brande,  and  the  chlorine 
test  of  Pelletier,  will  not  distinguish  always  between  quinine 
and  quinidine. 
The  presence  of  so  much  water  and  ammonia  is  detrimental  to 
the  British  Pharmacopoeia  test,  which  is  anything  but  a  good 
modification  of  Liebig's  original  one. 
From  these  remarks  it  will  be  apparent  that  a  good  qualita- 
tive test  for  detecting  the  several  cinchona  alkaloids  in  an  un- 
known mixture  is  a  desideratum.  From  a  considerable  series  of 
experiments  it  appears  that  these  conditions  may  be  amply  ful- 
filled by  either  of  the  two  following  methods  : 
The  first  is  a  modification  of  that  proposed  by  Liebig. 
Into  a  glass  tube  or  bottle  put  ten  grains  of  the  suspected 
salt,  dissolve  in  ten  minims  of  dilute  sulphuric  acid  and  60  min- 
ims of  distilled  water ;  to  this  add  150  minims  of  pure  sul- 
phuric ether,  three  minims  of  alcohol,  and  40  minims  of  a  so- 
lution of  hydrate  of  soda  (1  part  to  12  parts).  Agitate  well 
and  lay  aside  for  12  hours,  when,  if  the  slightest  trace  of  quini- 
dine, cinchonine,  or  cinchonidine  be  present,  they  will  be  seen 
at  the  line  of  separation  between  the  ether  and  solution  of  sul- 
phate of  soda. 
If  only  a  small  percentage  of  quinidine  be  present,  it  will  ap- 
pear as  an  oily  substratum,  appearing  under  the  lens  as  dust 
from  the  minuteness  of  its  particles.  Cinchonine  will  appear 
more  decidedly  crystalline.  With  a  little  practice,  the  eye  will 
easily  distinguish  which  of  the  alkaloids  is  deposited. 
This  will  detect  a  much  less  quantity  of  quinidine  than 
the  Pharmacopoeia  test.  In  the  latter  the  ether  dissolves  a 
greater  portion  of  the  quinidine,  while  the  dilute  ammoniacal 
solution  of  sulphate  of  ammonia  is  an  actual  solvent,  unless 
great  care  be  taken  to  add  no  more  ammonia  than  will  exactly 
precipitate  the  alkaloids,  which  is  often  difficult  and  tedious. 
The  second  method  proposed  is  the  one  most  generally  used 
by  the  author,  and  which  is  perhaps  the  easiest  and  most 
