452 
Assay  of  Iodoform. 
f  Am.  jour.  Pharin. 
\     October,  1910. 
extraction  with  water  present,  the  temperature  of  the  distilling 
flask  must  be  carefully  controlled  or  it  will  rise  to  such  a  point 
that  when  the  ether  siphons  over  and  comes  in  contact  with  the 
hot  water  it  will  vaporize  so  rapidly  that  there  is  great  danger  of 
loss.  There  is  no  trouble  of  this  kind  if  alcohol  only  is  used. 
The  following  is  the  process  in  detail  as  finally  adapted  to  the 
assay  of  iodoform. 
The  iodoform  is  added  to  50  c.c.  1/10  normal  silver  nitrate  V.S., 
to  whir  [1  has  been  added  3  c.c.  nitric  acid,  U.S. P.,  50  c.c.  alcohol 
is  added,  the  whole  being  contained  in  a  250  c.c.  florence  flask.  The 
flask  is  now  connected  with  a  reflux  condenser  and  heat  applied 
so  that  it  boils  gently.  The  heating  is  best  conducted  by  placing 
the  flask  in  a  water-bath  so  that  the  water  in  the  bath  is  about 
on  a  level  with  the  water  in  the  flask.  This  procedure  avoids 
any  bumping  or  spattering.  The  heat  is  continued  for  one-half 
hour  after  the  boiling  commences.  After  allowing  the  flask  to 
cool,  water  is  added  to  make  about  150  c.c,  a  little  ferric  ammonium 
sulphate  T.S.  added,  and  the  excess  silver  nitrate  V.S.  determined 
with  potassium  sulphocyanide  V.S.  Each  c.c.  1/10  normal  silver 
nitrate  V.S.  is  equivalent  to  0.0130  Gm.  iodoform.  The  following 
experiments  demonstrate  the  accuracy  of  the  method. 
A  sample  of  iodoform  was  first  procured  of  good  quality  and 
its  purity  determined  by  the  Carius  method.  This  sample  was 
used  in  all  of  the  experiments  recorded  below. 
Iodoform  taken.    Silver  iodide  weighed.    Iodoform  found.    Per  cent.  pure. 
O.701 1  1. 2631  O.7048  IOO.52 
The  sample  was  then  assayed  by  the  method  as  given  above. 
0-5352 
0.9632 
0.5382 
100.56 
Iodoform  taken. 
0-3375 
Iodoform  found. 
O.3386 
O.2017 
O.1819 
O.2095 
Per  cent.  pure. 
IOO.33 
IOO.29 
IOO.27 
IOO.05 
O.201 1 
O.1814 
O.2094 
The  principle  is  applied  to  the  assay  of  gauze  as  follows : 
The  gauze  is  placed  in  a  Soxhlet  extractor  of  about  60  c.c. 
capacity  and  the  entire  apparatus  connected  as  usual,  except  that  a 
