Am.  Jour.  PMrm.i       Sulphurous  Acid  in  Lime  Juice. 
December,  1909.  J  r 
563 
juice,  0.008  per  cent.  S02  was  apparently  found.  The  juice  was, 
however,  quite  free  from  any  added  S02. 
Lime  juice  holds  in  solution  a  small  quantity  of  essential  oil 
which  passes  over  on  distillation  and  combines  with  part  of  the 
iodine,  which  accounts  for  the  results  obtained.  The  samples  of 
juice  in  question  evidently  contained  more  oil  in  solution  than  the 
juice  expressed  by  the  writer.  This  is  explained  by  the  fact  that 
on  the  large  scale  a  greater  pressure  is  used  and  more  oil  expressed 
than  is  the  case  when  an  ordinary  lemon  press  is  used.  The  follow- 
ing experiments  prove  that  this  is  the  case.  The  juice  was  tested 
before  and  after  extraction  with  chloroform. 
100  c.c.  Lime  Juice  Taken 
No.  1  No.  2  No.  3 
(juice  expressed  by 
the  writer) 
C.c.  T%  iodine  consum- )         ^  „  „  „  „ 
•         [  070C  7TOO 
ed  before  extraction  V     n  ~  cr.  ~  cr.  ■£  ^ 
with  chloroform      J  =°-°2I4  %  S02     =0.0227  %  S02      =0.008  %  S02 
C.c.  Tn7T iodine  consum- )  , 
ed  ^fter  extraction        n  qo        n  1 '^%n 
with  chloroform      j  =°-°°32  %  S02     =0.0056  %  S02 
The  above  results  show  that  the  small  quantity  of  essential  oil 
held  in  solution  is  sufficient  to  render  the  official  method  useless 
in  the  case  of  lime  juice. 
After  a  number  of  experiments  the  following  qualitative  and 
quantitative  methods  were  worked  out  and  proved  to  be  reliable. 
QUALITATIVE  METHOD  FOR  THE  DETECTION  OF  S02  IN  LIME  JUICE. 
One  hundred  c.c.  of  lime  juice  is  acidified  with  5  c.c.  of  20  per 
cent,  phosphoric  acid,  and  50  c.c.  distilled  into  25  c.c.  of  a  1  per  cent, 
solution  of  sodium  bicarbonate  contained  in  a  Fresenius  or  other 
absorption  flask;  the  latter  is  attached  to  the  end  of  the  condenser 
by  a  perforated  cork.  The  distillate  is  placed  in  a  200  c.c.  Erlen- 
meyer  flask,  a  few  pieces  of  zinc  and  8  c.c.  of  hydrochloric  acid 
added.  A  plug  of  cotton  wool  is  inserted  in  the  neck  of  the  flask 
and  the  mouth  of  the  latter  capped  with  lead  acetate  paper.  After 
thirty  minutes  the  paper  is  removed  and  examined ;  if  any  S02 
is  present,  the  latter  will  be  stained  a  dark  brown  or  black. 
On  testing  the  sample  in  question  by  the  above  method,  the 
lead  paper  remained  unaffected.    Sulphurous  acid  (in  the  form  of 
