A^ebJrTa^rVT^8a9^7m•}     Volumetric  Estimation  of  Acetone.  69 
MM.  F.  Robineau1  and  G.  Rollin,  in  1893,  proposed  another  volu- 
metric method  for  estimating  acetone.  This  method  was  first 
brought  to  the  writer's  notice  through  the  generosity  of  Dr.  Squibb 
and  the  kindness  of  his  chemist,  Dr.  L.  L.  Jackson,  while  visiting 
the  laboratory  of  the  former  last  summer.  Prior  to  this  time 
Messinger's  process  had  been  used  exclusively  by  the  writer.  R. 
and  R.'s  method  is  applied  by  mixing  an  aqueous  acetone  solution 
with  a  strongly  alkaline  solution  of  potassium  iodide  and  convert- 
ing the  acetone  into  iodoform  by  means  of  a  titrated  solution 
of  sodium  hypochlorite,  the  end  reaction  being  determined  by 
means  of  a  bicarbonated  starch  solution. 
The  writer  has  not  applied  the  above  process  to  any  extent,  but 
has  studied  and  worked  with  Dr.  Squibb's2  modification  of  the  same 
considerably. 
The  solutions  required  for  this  modification  and  the  methods 
of  preparing  them  are  as  follows  : 
Pure  acetone  made  by  the  bisulphite  process. 
An  alkaline  solution  of  potassium  iodide.  Dissolve  250  grammes 
of  pure  potassium  iodide  in  distilled  water  and  make  up  to  1  litre. 
Dissolve  257  grammes  of  sodium  hydroxide,  purified  by  alcohol,  in 
distilled  water  and  make  up  to  1  litre.  Allow  the  insoluble 
part  to  subside  and  mix  850  c.c.  of  the  clear  solution  with  the  litre 
of  potassium  iodide. 
Solution  of  hypochlorite,  containing  about  2^  per  cent,  of 
available  chlorine.  To  each  litre  add  25  c.c.  of  sodium  hydroxide 
solution,  specific  gravity  1-29. 
Bicarbonated  starch  solution.  Treat  0-125  gramme  of  starch 
with  5  c.c.  of  cold  water,  then  add  20  c.c.  of  boiling  water 
and  boil  a  few  minutes,  cool  and  add  2  grammes  of  sodium 
bicarbonate.  The  keeping  quality  of  this  solution  is  certainly 
an  agreeable  surprise.  A  sample  prepared  four  months  ago  is  as 
delicate  to-day  as  a  freshly  prepared  one. 
The  manner  of  application.  Prepare  an  aqueous  solution  of  the 
pure  acetone  of  such  a  strength  that  each  10  c.c.  contains  exactly 
yL-  gramme  of  the  acetone.    Of  this  solution,  accurately  measure, 
1  1893,  Moniteur  Scientifique  (4),  7,  pt.  1,  272  ;  translation  in  J.  Am.  Chem. 
Soc,  is,  1068. 
2  1896,  J.  Am.  Chem.  Soc,  is,  1068. 
