428 
Atmospheric  Ozone. 
( Am.  Jour.  Pharrn. 
\  September,  1900. 
The  potassium  iodide  solutions  were  treated  with  a  very  dilute 
hydrochloric  acid  (2  c.c.)  and  starch  paste  (2  c.c),  and  then  were 
titrated  with  Tfo  normal  sodium  hyposulphite  V.  S.,  according  to 
pharmacopoeia!  directions.  This  method  is  based  on  the  following 
reactions,  given  by  Schwanert  (Pharm.  Chew.,  I,  292): 
3l2  +  6KOH  +  302 
3O3  +  6KI  +  3H20  = 
Add  to  this, 
5KI  +  KIO3  +  3H20 
6HCI 
3l2  -I-  6KC1  +  3H0O 
Hence,  3l2  equals  3O3,  or  I2  equals  03,  or  253-06  grammes  iodine 
equals  47-88  grammes  ozone,  or  1  gramme  iodine  equals  0-1889- 
0-1890  gramme  ozone. 
One  cubic  centimetre  normal  hyposulphite  V.  S.  equals 
OOO12653  gramme  iodine. 
One  gramme  iodine  equals  0-1889  gramme  ozone;  hence,  1  c.c. 
Y^j-  normal  hyposulphite  V.  S.  equals  0*000239  gramme  ozone. 
As  in  the  case  of  the  arsenite,  the  figures  given  in  the  following 
table  are  for  the  difference  only,  and  the  results  are  expressed  in 
milligrammes.  The  accuracy  of  this  iodide  assay  has  been  ques- 
tioned, but  the  close  similarity  of  its  results  to  those  from  the 
arsenite  assay  leads  us  to  believe  that  both  methods  are  reliable. 
The  results  of  the  fifteen  assays  are  tabulated  below  : 
Table  No.  I. 
TABLE  OF  ESTIMATIONS  WITH  SOLUTION  OF  POTASSIUM  ARSENITE. 
Solution 
No. 
Date. 
"Litres  of 
Air  Passed. 
Hours  in 
Passing. 
Difference 
in  Cubic 
Centimetres 
of 
i  I.  V.  s. 
40 
Ozone 
(Milli- 
grammes) 
Indicated. 
Ozone 
(Milli- 
grammes) 
per  100 
Litres  of  Air 
I  
February  zt 
37-640 
7' 
•40 
•24 
•63 
II  
24 
68-210 
9*25 
•65 
■39 
*57 
26 
78-672 
10-5 
•20 
•12 
•15 
IV  
27 
37-400 
8- 
•70 
•42 
I'I2 
•V  ....{ 
28 
to  March  i 
}  97752 
16-75 
•70 
•42 
*43 
*VI  
"  20 
77-876 
9' 
•40 
•30 
*VII  .... 
"  21 
77'65i 
9' 
4*30 
2-57 
3"30 
*VIII  .... 
"  22-23 
73*246 
I5'5 
4*20 
2*52  | 
3*45 
*IX  
"  26-29 
349'637 
70- 
•50  1 
•30 
0*085 
