70  Volumetric  Estimation  of  Acetone.  {^rebruarVTisw™" 
with  a  pipette,  10  c.c.  into  a  50  c.c.  beaker,  add  20  c.c.  of  the  alka- 
line potassium  iodide  solution  and  mix  well.  To  this  mixture  add, 
from  a  burette,  while  vigorously  agitating  the  contents  of  the  beaker, 
the  standard  solution  of  sodium  hypochlorite  in  rapid  drops  until 
about  9  c.c.  have  been  run  in.  Allow  the  iodoform  to  subside* 
which  it  does  rapidly,  then  add  a  drop  or  two  of  the  hypochlo- 
rite solution  ;  should  a  cloudiness  result,  add  another  y2  c.c.  of 
the  hypochlorite  solution  ;  agitate  well ;  allow  the  iodoform  to  sub- 
side, etc.,  until  just  a  faint  turbidity  results  on  adding  the  hypo- 
chlorite solution.  Now  agitate  the  solution  well  ;  transfer  a  small 
drop  to  a  white  porcelain  tile  ;  in  a  similar  manner,  bring  a  drop 
of  the  bicarbonated  starch  solution  near  this  drop,  then  connect  the 
two  drops  by  means  of  a  glass  rod.  If  a  blue  color  does  not 
develop  at  the  point  of  union,  not  enough  of  the  hypochlorite  solu- 
tion has  been  added.  Continue  adding  the  hypochlorite  solution, 
a  small  quantity  at  a  time,  agitating  and  testing,  until  a  blue  line 
is  just  formed  at  the  meeting  of  a  drop  of  the  starch  solution  and 
a  drop  of  the  mixture  titrated.  Ordinary  starch  solution  is  value- 
less for  this  end  reaction. 
The  number  of  c.c.  of  the  hypochlorite  solution  required  to  com- 
plete the  reaction  is  the  amount  of  this  active  agent  needed  to  con- 
vert gramme  of  acetone  into  iodoform.  From  this  basis  calcu- 
lations for  any  amount  of  acetone  are  readily  made. 
In  estimating  the  amount  of  acetone  in  any  solution,  first  prepare 
an  aqueous  solution  containing  from  1  to  2  per  cent,  of  acetone  by 
weight,  then  proceed  as  above  for  establishing  the  standard  with 
pure  acetone.  For  fuller  details  the  reader  is  referred  to  the  origi- 
nal communication. 
The  two  latter  methods  will  meet  with  two  objections :  first,  a  pure 
acetone,  and  second,  the  tedious,  time-consuming  drop  end  reaction. 
Pure  acetone  is  not  so  readily  prepared.  It  necessitates  the  prepa- 
ration of  an  acetone  absolutely  free  from  other  ketones,  before  the 
bisulphite  process  can  be  applied.  The  writer  has  not  been  able  to 
secure  acetone  that  assayed  more  than  9973  per  cent,  of  pure  ace- 
tone by  either  Messinger's  process  or  the  one  presently  to  be 
described.  This  small  quantity  may  have  volatilized,  but  the  loss 
would  be  practically  constant  for  all  the  methods,  consequently,  the 
basis  of  calculation  for  the  pure  acetone  methods  would  be  100, 
when  in  reality  it  is  less.    The  difference  may  again  be  due  to  some 
