Chlorinated  Soda  Solution. 
(Am.  Jour.  Pharm. 
t      April,  1910. 
Recently,  a  chlorinated  soda  solution  containing  about  6  per 
cent,  available  chlorine  was  required  in  the  course  of  some  experi- 
ments in  the  Division  of  Pathology  and  Bacteriology  of  the 
Hygienic  Laboratory  and  the  writer  was  requested  to  prepare  such 
a  solution.  A  trial  of  the  present  U.S. P.  method,  using  of  course 
proportionately  larger  quantities  of  the  required  substances,  showed 
that  this  method  is  inadequate  to  yield  a  chlorinated  soda  solution 
of  such  high  available  chlorine  content.  The  preparation  of  such 
a  solution  by  direct  passage  of  chlorine  gas  into'  a  solution  of  sodium 
hydroxide  suggested  itself,  and  in  looking  up  the  chemical  literature 
on  the  subject  it  was  found  that  such  a  method  has  actually  been  em- 
ployed by  Graebe  1  and  with  very  good  results.  Thus  Graebe  found 
that  by  employing  a  slight  excess  of  the  alkaline  solution  the  stability 
of  .the  resulting'  hypochlorite  is  much  increased;  for  example,  if 
instead  of  using  just  sufficient  sodium  hydroxide  to  combine  with  the 
chlorine,  i.e.,  in  the  theoretical  proportion  of  Cl2  to  2  NaOH,  we  use 
these  constituents  in  the  proportion  of  Cl2  to  2^4  NaOH,  he  found 
that  instead  of  a  solution  of  over  5  per  cent,  available  chlorine  losing 
practically  its  entire  available  chlorine  at  the  end  of  3  days,  it  will 
still  show  the  presence  of  5.03  per  cent,  available  chlorine  even  at  the 
end  of  6  days  and  although  the  temperature  had  risen  from  180  C.  to 
25 0  C.,  if  prepared  so  as  to  conform  to  the  latter  proportion ;  while  by 
employing  the  chlorine  and  the  sodium  hydroxide  in  the  proportion  of 
Clo  to  3  NaOH,  the  resulting  hypochlorite  solution  which  imme- 
diately after  preparation  contained  5.7  per  cent,  available  chlorine 
still  showed  the  presence  of  5.37  per  cent,  available  chlorine  even 
after  having  stood  23  days,  during  which  time  the  temperature  rose 
from  180  C.  to  25 0  C.  The  effect  of  light,  however,  he  found  unfav- 
orable to  its  stability  and  he  therefore  recommends  that  such  solu- 
tions be  kept  in  the  dark.  Graebe  further  points  out  the  advantages 
of  the  method  2  for  preparing  chlorine  that  is  based  on  the  reaction 
between  hydrochloric  acid  and  potassium  permanganate.  Thus  owing 
to  the  fact  that  this  reaction  is  practically  quantitative  it  is  possible 
to  prepare  hypochlorite  solutions  of  definite  strengths  by  using  the 
calculated  amounts  of  the  respective  substances  required.  The 
chlorine  thus  obtained  is  also  free  from  chlorine  dioxide ;  and  it 
is  possible  to  carry  out  the  whole  process  of  generating  the 
1Ber.,  35,  2753-2756  (1902). 
2Bcr.,  35,  43-45  (1902). 
