THE  AMEEIOAN 
JOURNAL  OF  PHARMACY 
DECEMBER,  ipop 
THE  DETECTION  AND  DETERMINATION  OF  SULPHUR- 
OUS ACID  IN  LIME  JUICE. 
By  Edwin  Dowzard. 
Some  time  ago  the  writer  had  occasion  to  examine  a  number 
of  samples  of  lime  juice  for  sulphurous  acid,  free  or  combined.  On 
applying  the  official  qualitative  and  quantitative  tests,  the  presence 
of  S02  was  indicated.    The  tests  are  as  follows : 
OFFICIAL  AND  PROVISIONAL  METHODS  OF  ANALYSIS,  BULLETIN  NO.  107 
(REVISED),  I908,  PAGE  187. 
(a)  Qualitative  Detection  of  S02. — "To  about  25  grammes 
of  the  sample  (with  the  addition  of  water  if  necessary),  placed  in 
a  200  c.c.  Erlenmeyer  flask,  add  some  sulphur-free  zinc  and  several 
cubic  centimetres  of  hydrochloric  acid.  In  the  presence  of  sulphites 
hydrogen  sulphide  will  be  generated  and  may  be  tested  for  with 
lead  paper.  Traces  of  metallic  sulphides  are  occasionally  present 
in  vegetables,  and  the  above  test  will  indicate  sulphites.  Hence 
positive  results  obtained  by  this  method  should  be  verified  by  the 
distillation  method." 
(b)  Determination  of  Total  S02  Distillation  Method  — 
"  Distil  100  grammes  (adding  water  if  necessary)  in  a  current  of 
carbon  dioxide  after  the  addition  of  about  5  c.c.  of  a  20  per  cent, 
solution  of  glacial  phosphoric  acid  until  50  c.c.  have  passed  over. 
Collect  the  distillate  in  n/10  iodine  solution  in  a  flask  closed  with  a 
stopper  perforated  with  two  holes,  through  one  of  which  the  end  of 
the  condenser  passes  and  through  the  other  a  U-tube  containing 
a  portion  of  the  standardized  iodine  solution.    Twenty-five  c.c.  of 
(561) 
