164 
Chlorinated  Soda  Solution. 
(  Am.  Jour.  Pharm. 
X      April,  1910. 
evolution  of  chlorine  commences  immediately  after  the  acid  and 
permanganate  come  in  contact,  and  the  rate  of  chlorine  generated 
is  easily  regulated  by  the  rate  of  flow  of  the  hydrochloric  acid. 
When  the  current  of  chlorine  was  observed  to  slow  down,  gentle 
heating  was  applied,  and  the  operation  continued  until  the  cur- 
rent of  chlorine  passing  the  Drexel,  washing  bottle  was  observed 
to  have  been  reduced  to  just  a  very  slow  bubbling.  The  cylinder 
and  contents  were  weighed  before  and  after  the  passage  of  the 
current  of  chlorine  and  the  increase  in  weight  was  found  to  be 
29  Gm.  This  would  make  the  added  chlorine  represent  5.81  per 
cent,  of  the  final  weight  of  the  solution.  An  actual  determination 
of  the  available  chlorine  in  this  solution,  carried  out  by  the  U. 
S.  P.  method,  showed  the  presence  of  5.80  per  cent,  available 
chlorine.  This  shows  therefore  that  the  chlorine  value  of  such 
a  solution  may  be  found  by  simply  determining  the  increase  in 
weight  due  to  its  passage  into  the  solution ;  and  it  also  shows 
that  perhaps  a  better  plan  to  follow  when  a  solution  of  a  given 
chlorine  strength  is  required  is  to  use  a  little  more  of  the  potassium 
permanganate  than  would  correspond  to  the  formula  10  Gm. 
KMn04  ==  1 1  Gm.  chlorine  and  determine  the  increase  in  the  weight 
of  the  solution  due  to  the  passage  of  the  chlorine  into  it;  when,  if 
the  solution  is  found  a  little  stronger  than  what  is  required,  it  could 
be  diluted  to  the  desired  strength  by  the  addition  of  the  calculated 
amount  of  the  sodium  hydroxide  solution.  It  would  seem  advisable 
therefore  that  Graebe's  method  for  the  preparation  of  chlorinated 
soda  solution  be  adopted  in  the  next  revision  of  the  U.S. P. ;  and 
perhaps  also  that  the  permanganate  method  for  chlorine  generation 
be  used  in  all  other  pharmacopceial  preparations  where  free  chlorine 
is  required,  as,  for  example,  in  the  preparation  of  chlorine  water. 
This  would  not  only  avoid  the  use  of  different  methods,  as  the 
chlorinated  lime  method  for  the  preparation  of  chlorinated  soda 
solution  and  the  chlorate  method  for  the  preparation  of  chlorine 
water,  but  would  also  yield  other  advantages.  Thus  the  latter  would 
then  be  pure  chlorine  water  instead  of  as  at  present  containing  also 
the  foreign  substances,  potassium  chloride  and  oxides  of  chlorine ; 
while  "  the  possible  danger  arising  in  the  preparation  of  chlorine 
from  either  sodium  or  potassium  chlorate  and  hydrochloric  acid," 
pointed  out  by  Merk 5  as  being  due  to  the  decomposition  with 
5  Proc.  A.  Ph.  A.,  52,  775  (1904). 
