148 
Identifying  Fats  and  Oils, 
(  Am.  Jour.  Puarm. 
t  >Tarch,1897. 
case,  it  must  be  brought  to  the  same  temperature.  As  the  action  of 
the  bromine  on  the  oil  is  instantaneous,  it  is  necessary  to  have  the 
thermometer  in  the  oil  solution  before  adding  the  bromine. 
The  bromine  being  largely  in  excess  of  the  amount  required,  the 
5  c.c.  of  the  solution  need  not  be  so  accurately  measured ;  we 
adopted  Dr.  Wiley's  apparatus  for  measuring  it  {Fig.  2). 
It  is  simply  a  wash  bottle  arrangement  ;  through  one  opening 
in  the  stopper  a  pipette  (graduated  on  the  stem  to  5  c.c.)  passes 
nearly  to  the  bottom,  through  the  other  a  short  tube  which  con- 
nects on  the  outside  with  an  atomizer  bulb ;  by  pressiug  this  bulb 
the  solution  is  forced  up  in  the  pipette  to  the  5  c.c.  mark ;  the  in- 
dex finger  is  then  used  to  close  the  top,  the  stopper  and  tube  are 
withdrawn  from  the  bottle,  the  point  of  the  pipette  directed  into  the 
oil,  and,  the  finger  being  withdrawn,  the  solution  flows  in. 
Our  experiments  proved  that  if  the  solution  was  allowed  to  run 
in  very  quickly  the  temperature  would  be  reduced,  in  some  instances* 
2°,  there  being  much  ebullition,  which  would  throw  the  hot  liquid 
against  the  cold  sides  of  the  tube  and  thus  reduce  the  temperature ; 
this  result  was  also  brought  about  by  stirring  the  mixture  with  the 
thermometer.  We  would,  therefore,  recommend  that  the  bromine 
solution  be  slowly  run  in,  consuming  about  a  half  minute  in  adding 
it.  The  figures  in  the  table  are  the  results  of  four  determinations 
on  each  oil,  the  average  of  these  being  given. 
In  making  the  tests  we  had  in  use  about  twelve  of  the  beaker 
test  tube  apparatus,  so  that  after  making  the  four  tests  the  tubes 
were  withdrawn  from  the  nests,  washed  out  with  petroleum  benzine 
and  inverted  so  that  they  would  dry.  For  the  next  set  of  tests  we 
took  four  more  tubes  and  beakers,  and  so  on,  until  we  had  used  all ; 
we  then  come  back  to  the  first  set,  having  them,  in  the  meantime, 
cleaned,  and  the  temperature  of  the  nest  reduced  to  that  of  the  room. 
Experiments  made  with  a  beaker  with  cotton  loosely  packed, 
without  any  magnesia,  proved  that  in  this  way  the  temperature 
was  also  considerably  lowered. 
In  the  table  will  be  found  Hehner  and  Mitchell's  figures  for  the 
oils  on  which  they  worked.  There  will  also  be  found  Dr.  Wiley's, 
who  worked  on  a  few  oils  in  the  laboratory  of  the  Washington 
Bureau  of  the  Department  of  Agriculture. 
We  are  still  at  work  on  this  subject,  and  hope  in  our  next  paper 
to  give  a  factor  which,  when  multiplied  by  the  rise  in  temperature 
of  the  oil,  will  approximately  give  Hubl's  iodine  number. 
