AFebruary^897?'}     Volumetric  Estimation  of  Acetone.  71 
slight  inaccuracies  in  the  volumetric  solutions.  Grant  that  abso- 
lutely pure  acetone  is  made,  it  is  not  readily  secured  when  desired. 
The  writer  has  adapted  Dr.  Squibb's  modification  so  that  both 
the  pure  acetone  and  the  drop  end  reaction  are  eliminated.  In  this 
process  the  following  solutions  are  employed : 
A  6  per  cent,  solution  of  hydrochloric  acid. 
The  alkaline  solution  of  potassium  iodide  of  Dr.  Squibb. 
A  decinormal  solution  of  sodium  thiosulphate. 
Sodium  hypochlorite  solution,  about  |-  normal,  or  containing  from 
2T6o"  t°  3  Per  cent-  °f  available  chlorine.  To  prepare  this  solution, 
intimately  mix  100  grammes  of  bleaching  powder  (35  per  cent.)  in 
400  c.c.  of  distilled  water.  Dissolve  120  grammes  of  crystallized 
sodium  carbonate  in  400  c.c.  of  hot  distilled  water,  and  immediately 
pour  the  latter  into  the  former.  Cover  the  vessel  and  allow  to  cool, 
then  decant  the  clear  liquid,  filter  the  remainder  and  to  the  filter 
add  enough  water  to  make  up  to  1  litre.  To  each  litre  add  25 
c.c.  of  sodium  hydroxide  solution,  specific  gravity  1-29. 
An  aqueous  solution  of  acetone  containing  from  1  to  2  per  cent, 
by  weight.  Prepared  as  for  Messinger's  process  above.  To  esti- 
mate the  acetone,  place  20  c.  c.  of  the  alkaline  potassium  iodide 
solution  into  a  suitable  flask  add  10  c.c.  of  the  diluted  aqueous  ace- 
tone solution,  or  weigh  if  greater  accuracy  is  desired ;  mix  well,  and 
run  in  from  a  burette,  while  rotating  the  flask,  an  excess  of  the 
sodium  hypochlorite  solution,  insert  the  stopple  quickly  and  shake 
well  for  one  minute.  After  agitating,  render  the  mixture  acid  by 
means  of  the  hydrochloric  acid  solution,  add,  while  rotating  the 
flask,  an  excess  of  the  sodium  thiosulphate  solution,  and  allow  the 
mixture  to  stand  a  few  minutes.  Then  add  the  starch  indicator  and 
re-titrate  the  excess  of  the  sodium  thiosulphate. 
The  relation  of  the  sodium  hypochlorite  solution  to  the  sodium 
thiosulphate  solution  being  known,  the  percentage  of  acetone  can 
readily  be  calculated  from  the  above  data.  One  atom  of  available 
chlorine  will  liberate  I  atom  of  iodine  from  the  potassium  iodide 
of  the  alkaline  solution,  or  I  c.c.  will  liberate  just  enough  iodine  to 
make  1  c.c.  of  iodine  solution  of  the  same  normal  strength  as  the 
sodium  hypochlorite  solution  originally  was  ;  therefore,  by  reading 
the  number  of  c.c.  of  sodium  hypochlorite  solution  consumed  as  so 
many  c.c.  of  iodine  solution  of  the  same  normal  strength,  we  reduce 
the  calculation  to  the  basis  of  iodine.  For  explanation  from  here 
see  Messinger's  process  above. 
