A  PROCESS  FOR  ESTIMATING  TANNIC  ACID  IN  GALLS.  429 
found  is  simply  multiplied  by  1-217  in  order  to  find  the  amount 
of  sulphate  present,  or  in  the  case  of  quinidine,  etc.,  by  the 
factor  1.333. 
A  mixture  of  4-80  grm.  of  pure  sulphate  of  quinine,  and  0-20 
grm.  of  pure  sulphate  of  quinidine,  were  separated  in  a  similar 
manner.  Total  amount  of  filtrate  =  50  c.  c.  25  c.  c.  were  pre- 
cipitated with  35  c.  c.  of  the  standard  ammonia  solution  of  0-96 
sp.  gr.,  and  gave  0-072  grm.  of  a  precipitate  ^X1'3^0*72  =  0-1919 
instead  of  0-20. 
If  the  composition  of  the  foreign  sulphate  is  not  known — 
which  is  generally  the  case — it  will  be  safer  simply  to  compare 
the  quantity  of  the  free  base  found  with  the  average  percentage 
of  pure  sulphate  of  quinine  =  75  per  cent.  (Freshly  re-crystal- 
lized sulphate  of  quinine,  dried  by  pressure  between  filter  paper 
without  application  of  heat,  contains  73-5  per  cent,  of  quinine.) 
8.  Examination  of  other  Officinal  Cinchona  Salts. — It  is  evi- 
dent that  the  ammonia  test  can  be  employed  likewise  in  the  es- 
timation of  cinchona  compounds,  which  are  more  soluble  than 
sulphate  of  quinine,  of  course  by  employing  other  proportions 
for  their  mixtures.  1  c.  c.  of  pure  hydrochlorate  of  quinine 
requires  ex.  gr.  22  c.  c.  of  the  ammonia  solution  of  sp.  gr.  0-92 
for  its  precipitation,  and  in  order  to  re-dissolve  the  alkaloid  in 
excess,  whilst  solutions  of  other  hydrochlorates  of  the  cinchona 
bases  ?annot  be  re-dissolved,  even  on  adding  a  large  excess  of 
ammonia.  In  examining  these  readily  soluble  salts  it  becomes 
necessary,  however,  first  to  dilute  measured  quantities  of  solu- 
tions, saturated  in  the  cold,  with  water  to  the  proportion  in 
which  sulphate  of  quinine  is  soluble,  before  adding  the  ammo- 
nia solution,  since  ammonia  precipitates  quinine  from  concen. 
trated  saline  solutions,  in  lumps  which  are  as  difficult  to  re-dis- 
solve when  they  have  once  been  precipitated,  as  are  the  foreign 
bases. — London  Pharm.  Journ.,  July,  1862,  from  Zeitschrift  fur 
Analytische  Chemie. 
A  PROCESS  FOR  ESTIMATING  TANNIC  ACID  IN  GALLS. 
By  Mr.  J.  H.  Marriage, 
Observing  that  your  number  for  the  present  month  contains 
a  process  for  estimating  Tannic  Acid,  I  venture  to  send  you  de- 
