AmN°ovr;?89o.rm"}    Iodine  Absorption  of  Essential  Oils.  571 
details  of  the  process  it  is  unnecessary  to  give,  simply  referring  to 
it  as  the  well-known  Hubl's  process  for  determining  the  iodine 
absorption  of  fixed  oils  and  fats. 
TIME  OF  DIGESTION. 
The  absorption  by  this  method,  as  applied  to  fixed  oils,  is  com- 
plete in  from  three  to  four  hours.  The  writer  seems  to  have  been 
the  only  analyst  who  performed  any  experiments  with  a  view  to 
fixing  the  proper  time  of  digestion  of  the  iodine  solution  and  essen- 
tial oil  before  titrating  to  determine  the  excess.  The  others  either 
ignored  the  question  or  assumed  that  it  was  completed  in  the  same 
time  as  is  the  case  with  fixed  oils.  Barenthin  digested  his  iodine 
solution  and  oil  together  for  "  three  or  four  hours."  Mr.  Williams 
makes  no  mention  of  the  time,  though  his  failure  to  specify  any 
different  time  would  lead  us  to  believe  that  he,  too,  took  the  usual 
time.  Mr.  Davies,  on  the  other  hand,  allowed  his  oils  to  stand  in 
contact  with  the  iodine  "  during  one  night,"  which  would  probably 
be  from  15  to  17  hours'  time.  The  writer  may  give  here  a  tabu- 
lated statement  of  the  results  of  determinations  for  different  periods 
of  time  : 
Tims  of  Digestion. 
3  hrs. 
6  hrs. 
15  hrs. 
24  hrs. 
40  hrs. 
48  hrs. 
Oil  Peppermint,  . 
21:1 
22-8 
24*5 
<  <          <  < 
179 
179 
<  t  <( 
no 
120 
no 
126! 
"  Bergamot,  .  . 
300 
345 
"  Orange  Peel 
(Bitter),  .  . 
321 
362 
"  Turpentine,  . 
291 
33  "3 
345 
353 
397 
"  Peppermint 
(Adult),  t.  . 
847! 
74'i  ! 
"  Peppermint 
(Adult),    .  . 
88-3! 
73 '6  ! 
"  Thyme,  .  .  . 
210  ! 
183! 
Thymol,  .... 
201 ! 
181  ! 
From  these  results,  and  some  observations  by  Mr.  Davies,  we 
may  infer  that  the  rate  of  absorption  is  not  equal  for  all  oils,  and 
perhaps  not  even  for  all  samples  of  the  same  oil.  Also,  it  is  evident 
