312  The  Estimation  of  Fat.  {Am,j5™'i9*5arm" 
denser.  There  was  thorough  saponification.  The  alcohol  was  boiled 
off  as  completely  as  possible.  The  solution  was  then  made  up  to  a 
litre  of  solution  with  water,  and  100  Cc.  aliquots  were  taken.  The 
petroleum  ether  extract  was  perfectly  colorless. 
Comparison  of  Results  by  Soxhlet  Extraction. 
As  mentioned  before,  no  ether-soluble  material  was  obtained  by 
extraction  of  the  dried  blood.  Twice  extraction  of  the  liver  (after 
drying  in  vacuo)  gave  2.723  per  cent,  of  ether-soluble  material. 
The  fresh  sample  of  clear  back  fat  of  pork  was  analyzed,  giving 
moisture  7.68  per  cent,  and  fat  (ether-soluble)  90.13  per  cent.  It 
will  be  noted  that  the  results  obtained  by  the  Soxhlet  extraction 
method  and  the  Kumagawa-Suto  method  do  not  agree. 
Lieberman  and  Szekely  6  have  proposed  a  metkod  which  consists 
in  saponification  of  the  fat,  acidifying  the  soap  with  sulphuric  acid. 
The  acidified  solution,  in  a  specially-graduated  flask,  is  shaken  with 
petroleum  ether  and  the  flask  filled  to  the  mark  with  a  saturated 
sodium  chloride  solution.  After  thorough  mixing,  an  aliquot  of  the 
petroleum  ether  layer  is  taken,  mixed  with  neutral  alcohol,  and 
titrated  with  standard  alcoholic  potash.  Phenolphthalein  is  used  as 
an  indicator.  The  soap  formed  is  evaporated  to  dryness,  weighed, 
and  the  results  are  calculated  to  neutral  glycerides. 
In  studying  this  method  in  comparison  with  the  other  methods, 
we  tried  some  modifications  which  seemed  to  be  advantageous,  and 
propose  the  following  method : 
Description  of  Proposed  Method. — The  sample  is  heated  for  two 
hours  with  30  Cc.  of  a  20  per  cent,  sodium  hydroxide  solution. 
Place  the  beaker  in  the  water-bath  and  cover  with  a  funnel  having 
the  stem  cut  oft".  During  this  saponification  the  mixture  is  stirred 
a  few  times. 
The  solution,  while  still  warm,  is  transferred  to  a  glass-stoppered 
separatory  funnel  of  about  300  Cc.  capacity.  The  beaker  is  washed 
out  two  or  three  times  with  warm  water.  The  solution  is  then  acidified 
with  35  Cc.  of  a  20  per  cent,  hydrochloric  acid  solution,  (specific 
gravity  1.1).  After  thorough  cooling  the  contents  of  the  separatory 
funnel  are  shaken  out  with  ether.  The  combined  portions  of  the 
ether  solution  are  filtered  and  evaporated  to  dryness  on  the  water- 
bath.    The  residue  is  next  taken  up  with  about  25  Cc.  of  fat-free 
6  L.  V.  Lieberman  and  S.  Szekely:  Arch.  f.  d.  ges.  Physiol.,  lxxii,  p.  360, 
1898. 
