512  Chloroform  in  Lozenges.  { ANovimberf wo?" 
5.  Potassium  Chromate  Solution,  U.  S.  P. 
6.  Standard  Silver  Nitrate  Solution.  (8.545  Gm.  of  silver  nitrate 
are  dissolved  in  water  and  made  up  to  1000  c.c.)  The  solution 
should  be  standardized  against  pure  sodium  chloride — 
(1  c.c.  =  0.002  Gm.  chloroform). 
One,  or  half  a  lozenge,  is  weighed  and  placed  in  a  200  c.c.  flask 
containing  70  c.c.  of  alcoholic  alkali.  The  flask  is  then  connected 
with  a  reflux  condenser  and  the  contents  heated  not  quite  to  boiling 
point  until  the  lozenge  dissolves  or  disintegrates.  The  liquid  is 
then  gently  boiled  for  45  minutes.  25  c.c.  of  water  are  added  to 
the  hot  liquid,  followed  by  four  drops  of  phenolphthalein  solution 
and  sufficient  dilute  nitric  acid  to  render  the  liquid  slightly  acid. 
0.5  Gm.  of  calcium  carbonate  is  then  added  and  the  contents  of 
the  flask  shaken.  After  cooling,  the  liquid  is  titrated  with 
standard  silver  nitrate  solution,  using  potassium  chromate  as 
an  indicator. 
A  correction  must  be  applied  for  the  chlorides  present  in  the 
reagents  and  lozenge.  70  c.c.  of  alcoholic  alkali  are  diluted  with 
25  c.c.  of  water  and  neutralized  with  dilute  nitric  acid,  0.5  Gm.  of 
calcium  carbonate  is  added  and  the  liquid  titrated  with  standard 
silver  nitrate  solution.  It  is  only  necessary  to  determine  this  cor- 
rection once  for  each  batch  of  reagents.  The  correction  for  chlorides 
in  the  lozenge  is  determined  as  follows :  One  lozenge  is  weighed 
and  dissolved  in  30  c.c.  of  hot  water,  a  slight  excess  of  nitric  acid 
added,  followed  by  0.5  Gm.  of  calcium  carbonate,  and  the  mixture 
titrated  with  standard  silver  nitrate  solution. 
The  corrections  for  the  reagents  and  lozenge  are  added  together 
and  subtracted  from  the  figure  obtained  in  the  chloroform  deter- 
mination, the  difference  representing  the  chlorine  present  as 
chloroform. 
The  accuracy  of  the  method  was  determined  as  follows :  1.8502 
Gm.  of  pure  chloroform  were  diluted  to  99.54  c.c.  with  alcohol, 
and  the  chloroform  determined  by  the  above  method  with  the 
following  results : 
Quantity  of  chloroformic 
solution  taken.  Chloroform  present.  Chloroform  found. 
2  C.C.  O.O3717  O.O364 
4  c.c.  0.07434  0.0700 
