400  Carrel-Dakin  Solution.  /  Am.  jour.  Pharm. 
■  *■    September,  1917. 
well  for  several  minutes.  Allow  to  stand  for  at  least  half  an  hour 
until  reaction  is  complete  and  then  siphon  oft  the  supernatant  liquor 
and  filter  through  paper.  The  solution,  undiluted,  is  then  ready 
for  use. 
When  the  chlorine  content  of  the  chlorinated  lime  is  above  or 
below  25  per  cent.,  the  proportions  of  the  three  ingredients  entering 
into  this  solution  must  be  increased  or  reduced  accordingly.  To 
avoid  the  necessary  calculation  that  this  entails,  Daufresne  has  pre- 
pared the  following  table : 
Quantities  of  Ingredients  for  Ten  Liters  of  Dakin's  Solution 
Titer  of  Chlorinated  Lime.  Anhydrous  Sodium  Sodium  Bicarbonate. 
Chlorinated  Lime.  Gm.  Carbonate,  Gm.  Gm. 
20  230  II5  96 
21  220  110  92 
22  210  105  88 
23  200  100  84 
24  192  96  80 
25  184  92  76 
26  177  89  72 
27  170  85  70 
28  164  82  68 
29  159  80  66 
30  154  77  64 
31  148  74  62 
32  144  72  60 
33  140  70  59 
34  135  68  57 
35  132  66  55 
36  128  64  53 
37  124  62  52 
It  would  be  well  to  take  the  titer  of  this  solution  occasionally.  The 
same  substances  used  for  determining  the  activity  of  the  chlorine 
in  the  lime  are  used  for  this  purpose. 
To  ten  mils  of  the  finished  solution  add  20  mils  of  10  per  cent, 
solution  of  potassium  iodide  and  2  mils  of  acetic  or  hydrochloric 
acid.  Measure  into  this  mixture,  drop  by  drop,  from  a  burette,  a 
decinormal  solution  of  sodium  thiosulphate  until  decoloration  is 
complete.  The  number  of  mils  used  multiplied  by  0.03725  will  give 
the  weight  of  the  sodium  hypochlorite  in  100  mils  of  the  preparation. 
In  order  to  determine  the  alkalinity  of  the  Carrel-Dakin  solution 
or  note  its  freedom  from  caustic  sodium,  add  to  20  mils  of  the 
solution  0.02  of  phenolphthalein ;  if  correctly  prepared  no  red  color- 
ation should  appear. 
