Am.  Jour.  Pharm.l 
September,  1900.  J 
Atmospheric  Ozone. 
427 
bulb  were  returned  to  the  original  bottle,  it  being  necessary  to 
employ  a  porcelain  capsule  for  this  purpose.  The  bulb  and  capsule 
were  repeatedly  washed  with  distilled  water,  the  washings  added  to 
the  solution  in  the  bottle  and  the  filled  and  securely  stoppered 
bottles  returned  to  Cleveland,  for  titration.  Of  each  separate  batch 
of  solutions  handled,  one  bottle  each,  of  the  iodide  and  of  the  arsen- 
ite, was  returned  to  Cleveland  as  it  had  been  sent — unopened. 
These  solutions,  as  well  as  the  original  solution  remaining  in  Cleve- 
land, were  used  as  control,  the  solutions  in  the  unopened  bottles 
having  undergone  all  the  vicissitudes  of  their  fellows,  save  the  actual 
absorption  of  air. 
To  each  of  the  potassium  arsenite  solutions  was  added  2  c.c.  of 
a  10  per  cent,  solution  of  ammonium  carbonate  and  2  c.c.  of  a  1 
per  cent,  starch  paste.  Then  it  was  titrated  with  normal  iodine 
V.  S.  It  was  noted  that  the  color  first  appearing  faded  after  about 
filteen  minutes,  and  a  few  extra  drops  were  added  to  give  a  lasting 
color. 
The  following  explains  the  calculation  of  the  amount  of  ozone : 
KAs02;  molecular  weight,  145-85.      03;  molecular  weight,  47-88. 
Since  one  molecule  of  ozone  is  required  to  convert  one  molecule 
potassium  arsenite  to  arsenate,  145-85  grammes  KAs02  equals  47-88 
grammes  ozone,  or  1  gramme  arsenite  equals  0-3287  gramme 
ozone. 
The  U.S.P.  says  that  1  c.c.  ^  normal  iodine  V.  S.  equals  0  004942 
gramme  As203,  and  since  2KOH  -j-  As203  =  2KAs02  -f  H20,  we 
deduce  that  1  c.c.  T^  normal  iodine  V.  S.  equals  0-007292  gramme 
KAs02;  the  molecular  weight  of  2KAs02  (2917)  being  to  that  of 
As2Os  (197-68)  as  0-007292  is  to  0-004942.  Since  1  c.c.  T^  normal 
iodine  V.  S.  equals  0-007292  gramme  KAs02,  and  since  I  gramme 
KAs02  equals  0-3287  gramme  ozone,  it  follows  that  1  c.c.  y1-^ 
normal  iodine  V.  S.  indicates  0-0023968804  gramme  ozone,  and  the 
difference  between  the  amounts  of  iodine  V.  S.  required  in  titrating 
the  original  solution  and  that  acted  upon  by  the  atmospheric  ozone 
indicates  the  amount  of  ozone  acting  upon  the  KAs02;  hence,  in 
the  table  given  below  only  the  difference  in  cubic  centimetres  is 
given,  it  being  understood  to  represent,  in  each  case,  a  diminution 
of  arsenite  and  increase  of  arsenate.  As  normal  iodine  V.  S. 
was  employed,  each  cubic  centimetre  in  the  table  indicates  but  J-  of 
0-0023968804,  or  0-00059922  gramme  ozone. 
