^'bra^iy  Pi9ai4m' }  Assay  Process  for  Quinine  in  Tablets.  55 
If  this  25  c.c.  of  filtrate  is  colorless  or  of  a  light  straw  color, 
transfer  it  to  a  tared  beaker  of  60-100  c.c.  capacity,  rinsing  the 
cylinder  with  three  portions  of  10  c.c.  of  chloroform  and  adding  the 
same  to  the  chloroform  solution  in  the  tared  beaker.  Then  evapo- 
rate the  chloroform  carefully  on  a  water  bath.  If  the  filtrate  is  highly 
colored,  from  the  coating,  coloring  matter,  or  resinous  substances  in 
the  tablets,  transfer  the  same  into  a  clean  separatory  funnel,  rinse 
out  the  cylinder  as  before,  adding  the  same  to  the  chloroform 
solution  in  the  separatory  funnel,  and  shake  out  with  three  portions 
of  normal  sulphuric  acid,  15,  5,  5  c.c.  respectively,  each  portion 
diluted  with  5  c.c.  of  distilled  water.  Collect  the  combined  acid 
aqueous  solution  in  a  clean  separatory  funnel,  add  a  small  piece  of 
red  litmus  paper,  make  distinctly  alkaline  with  ammonia  water 
U.  S.  P.  and  shake  out  with  three  successive  portions  of  25,  15,  and 
15  c.c.  of  chloroform,  collecting  the  same  in  a  tared  beaker.  After 
the  chloroform  has  evaporated,  redissolve  the  residue  in  5  or  10  c.c. 
of  ether  and  let  evaporate  spontaneously. 
Finally,  place  the  tared  beaker,  containing  the  quinine  residue  in 
a  drying  oven  and  heat  to  a  constant  weight  at  1250  C,  cooling  the 
tared  beaker  each  time  in  a  desiccator  before  weighing.  It  usually 
requires  from  one  to  three  hours  of  heating  until  the  weight  is  con- 
stant. The  tared  beaker  should  be  chemically  clean  and  heated  for 
at  least  one  half  hour  at  125 0  C.  and  cooled  in  a  calcium  chloride 
desiccator,  before  it  is  weighed  and  the  chloroformic  solution  added. 
If  exactly  10  grains  of  quinine  or  the  salts  of  quinine  were  taken 
as  per  label  the  residue  should  weigh  the  following : 
For  Quinine  Alkaloid  U.  S.  P.  (Quinine  +  3H00)   0.5553  Grams. 
For  Quinine  Bisulphate  U.  S.  P   0.3830  Grams. 
For  Quinine  Hydrobromide  U.  S.  P   0.4963  Grams. 
For  Quinine  Hydrochloride  U.  S.  P   0.5296  Grams. 
For  Quinine  Salicylate  U.  S.  P   0.4457  Grams. 
For  Quinine  Sulphate  U.  S.  P   0.4814  Grams. 
Tablets  containing  substances  like  calcined  magnesia  as  a  drying 
agent,  do  not  filter  rapidly  by  the  above  method.  The  water  in  the 
ammonia  water  forms  a  gelatinous  mass  with  the  magnesia,  which 
prevents  rapid  filtration  and  sometimes  stops  it  altogether.  In  that 
case  the  following  method  is  suggested.  Measure  out  in  a  50  c.c. 
measuring  cylinder,  5  c.c.  of  spirit  of  ammonia  U.  S.  P.,  add  a 
sufficient  quantity  of  chloroform  to  make  exactly  50  c.c.  Use 
