Am.  Tour.  Pharm.  \ 
December,  1917.  -* 
Sodium  Benzoate. 
579 
water  in  the  cylinder  D.  The  flask  is  now  slowly  heated  with  a 
gas  burner  and  constantly  agitated,  not  too  strongly,  but  just  enough 
to  keep  the  contents  in  motion  until  boiling.  The  boiling  is  inter- 
mittently continued,  with  occasional  agitation,  for  3  to  5  minutes, 
when  all  chlorine  is  distilled  over  into  the  KI  solution.  The  boiling 
is  stopped,  the  flask  quickly 
removed,  and  the  glass  tubing 
washed,  inside  and  outside, 
into  the  main  solution,  which 
is  transferred  into  a  600  Cc. 
pear-shaped  flask,  then  brought 
to  a  volume  of  about  200  Cc. 
and  titrated  with  a  N/10  so- 
dium thiosulphate  solution  pre- 
viously standardized  against 
pure  iodine.  One  equivalent 
of  iodine  is  equal  to  one  equiva- 
lent of  chlorine :  1  Cc.  iV/10 
Xa2S203  =  0.003546  Gm.  CI. 
When  a  liquid  is  to  be  an- 
alyzed, the  manganese  dioxide 
is  simply  added  to  the  sample 
in  the  flask. 
If  the  chlorine  in  fluorides 
is  to  be  determined  the  pro- 
cedure is  carried  out  in  the 
same  way  as  for  the  other 
samples.  Some  HF  will  be  evolved,  but  it  has  no  effect  upon  the 
final  results  and  its  action  upon  the  glass  is  negligible. 
If  the  sulphuric  acid  is  free  from  nitric  and  hydrochloric  acids, 
chlorides,  nitrates  and  nitrous  fumes,  and  the  manganese  dioxide  con- 
tains no  impurities  capable  of  decomposing  KI  on  volatilization,  the 
boiling  of  the  sulphuric  acid  and  AlnOo  for  over  8  or  10  minutes  does 
not  produce  any  appreciable  coloration  in  the  KI  solution.  The  sul- 
phuric acid  may  be  heated  to  fuming  to  drive  of  HNOs,  otherwise  a 
blank  test  can  be  run  and  appropriate  correction  made.  The  highest 
blank  consumption  of  AT  10  Xa2S2Os  did  not  run  over  0.2  Cc.  in  the 
author's  experience  and  this  was  due  to  nitric  acid  found  in  the  sul- 
phuric acid  used. 
Apparatus  for  the  Determination 
of  Chlorine  in  Chlorides 
by  Distillation. 
