72  Volumetric  Estimation  of  Acetone.  {AFebJr°uaryP?8OTm* 
Example  of  calculation.  Ten  c.c.  of  the  acetone  solution,  con- 
taining i  gramme  of  the  solution  to  be  analysed,  required  14*57  c  c- 
of  N  X  0  806  sodium  hypochlorite  solution,  which  formed  14-57  c.c. 
of  iodine  solution  of  the  same  strength  ;  or  combining  we  have : 
I4-57  X  0  806  X  0-1265  X  0-07612 
 ~  :         =  amount  of  acetone  = 
I  gramme  of  solution. 
1 1-307  per  cent. 
On  comparing  Messinger's,  Dr.  Squibbs'  and  the  writer's  adapta- 
tion with  the  same  solution,  the  following  results,  in  per  cent,  were 
obtained  : 
Messinger. 
Squibb. 
Author. 
Pure  acetone   
99-69 
99-95 
99-73 
Residue  8o°  C.  and  above  . 
20 -oo 
19-67 
20*39 
Purified  by  fraction    .  .  . 
99'03 
99-00 
99-41 
Commercial  acetone  .  .  . 
96-23 
96-00 
96-63 
<<  '  «< 
98-00 
97-83 
97-93 
<  <               <  t 
94-30 
94-00 
94-46 
94-80 
94-70 
94-81 
<<  << 
97-12 
96-23 
96*42 
«<               <  < 
94-93 
94-80 
94-39 
<  (               1  < 
96-b8 
96-56 
96*79 
<<  a 
97-32 
97-28 
97-45 
90-74 
89-03 
90-51 
<  <                      <  ( 
98-82 
96-11 
98-62 
((                      <  < 
92-32 
92*20 
92-94 
Wood  alcohol   
14-61 
14-49 
1478 
n-8i 
1 1 73 
12-00 
Crude  wood  alcohol    .  .  . 
11-23 
11*00 
II-42 
The  above  table  clearly  shows  that  the  results  obtained  by  Dr. 
Squibb's  process  are  a  trifle  too  low,  notwithstanding  the  fact  that 
its  basis  of  calculation  gives  it  some  advantage.  The  method  is 
represented  to  yield  satisfactory  results  for  ordinary  work,  and  that 
it  certainly  does.  The  difficulty  with  this  method  lies  in  the  end 
reaction.  According  to  some  experiments  made  by  the  writer,  it  is 
necessary  to  have  present  a  larger  excess  of  the  active  agent,  to 
bring  about  the  completed  reaction,  than  the  end  reaction  allows. 
The  iodoform  reaction  with  ethyl  alcohol  is  an  endothermic  one, 
consequently  its  presence  does  not  interfere  with  the  estimation  of 
acetone,  which  does  not  require  the  presence  of  external  heat  to 
bring  about  the  reaction.  The  same  holds  true  for  all  other  groups 
of  endothermic  reaction. 
