572 
Iodine  Absorption  of  Essential  Oils. 
Am  Jour.  Pharm. 
Nov.,  1890. 
that,  in  many  instances,  the  absorption  is  not  complete  within  a 
period  of  twenty-four  to  forty-eight  hours;  though  in  four  instances 
the  longer  digestion  shows  less  absorption  than  the  shorter  period. 
This  same  phenomenon  was  also  noticed  later  in  the  case  of  turpen- 
tine with  simple  chloroform  solution  of  iodine. 
These  experiments  are  not  in  themselves  sufficient  to  fix  the 
proper  length  of  time  in  which  the  oils  and  iodine  should  remain  in 
contact,  but  in  the  writer's  work  40  to  48  hours  was  at  first  allowed. 
This,  however,  is  too  long  for  practical  purposes,  and  a  conventional 
time  will  probably  have  to  be  adopted.  The  "  standing  over  night," 
or  a  period  of  about  16  hours,  recommends  itself  to  the  writer,  and 
in  recent  work  has  been  followed. 
COMPARISON. 
In  the  following  tables,  the  results  obtained  by  the  different 
operators  are  placed  side  by  side  for  comparative  purposes.  It  must 
be  borne  in  mind  that  the  difference  in  time  allowed  by  the  different 
operators  may  produce  different  figures.  Mr.  Williams  and  Mr. 
Barenthin  having  evidently  operated  during  the  same  length  of 
time ;  it  is  possible  to  compare  their  results.  The  writer's  later 
work,  however,  that  in  the  fourth  column,  was  performed  with  about 
sixteen  hours'  digestion  ("  over  night "),  and  can,  therefore,  be 
compared  with  that  of  Mr.  Davies.  The  number  of  oils  examined 
was  limited,  but  I  may  say  that  those  given  in  column  four  were  of 
my  own  distillation,  and  their  purity  is  therefore  assured. 
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