The  Estimation  of  Fat. 
f  Am.  Jour.  Pharm. 
\       July,  1915. 
extracted  with  petroleum  ether,  and  filtered.  The  nitrate  is  evapo- 
rated and  dried  to  constant  weight.  The  weight  of  unsaponifiable 
material  will  give  by  subtraction  the  true  amount  of  fatty  acids 
which  is  reported  as  fat  by  multiplying  by  the  factor  1.046.  This 
method  has  been  shown  to  give  very  satisfactory  results  on  many 
substances,  but  has  not  worked  satisfactorily  with  blood. 
Shimidzu  3  has  modified  the  above  method  for  work  with  blood. 
He  first  extracts  the  blood  with  95  per  cent,  alcohol  and  filters  through 
a  cloth  filter.  The  residue  is  again  extracted  with  boiling  alcohol. 
The  combined  alcoholic  filtrates  are  saponified  with  5N  sodium 
hydroxide,  and  the  determination  is  continued  as  directed  by  Kuma- 
gawa-Suto.  Following  these  directions  we  made  several  deter- 
minations of  fat  in  cow's  blood  with  the  following  results: 
Table  I. 
Blood. 
Weight  of 
sample 
Weight  of 
fatty  acids 
and  unsaponi- 
fiable sub- 
stances 
Weight  of 
unsaponifiable 
substances 
Weight  of 
fatty  acids 
Weight  of 
neutral  fat 
Neutral 
fat 
Time  on 
fvater- 
bath 
Grammes 
Gramme 
Gramme 
Gramme 
Gramme 
Per  cent. 
Hours 
20 
0.1775 
O.0813 
O.0942 
O.O985 
0-493 
X 
20 
O.I785 
0.0935 
O.085O 
O.0889 
0.445 
20 
0.1523 
O.0967 
O.0556 
O.O582 
0.291 
6 
10 
O.O782 
O.O471 
0.03 1 1 
O.O325 
0.325 
3 
9.5 
O.O757 
0.0353 
O.O404 
O.O423 
O.444 
4 
Average  of  five  determinations,  0.3996  per  cent. 
Greatest  variation  from  average,  28  per  cent. 
Least  variation  from  average,  11  per  cent. 
As  can  be  seen  from  the  above  table,  the  results  are  far  from  satis- 
factory. The  great  difference  in  the  results  may  be  due  to  several 
causes.  The  large  number  of  filterings  may  cause  a  considerable  loss. 
The  great  amount  of  cholesterol  and  other  unsaponifiable  substances 
in  the  blood  may  cause  a  difficulty  in  separating  them  from  the  fatty 
acids.  Furthermore,  it  seems  almost  impossible  to  get  rid  of  all  the 
coloring  matter.  Even  after  six  hours'  drying  we  were  unable  to 
obtain  a  colorless  filtrate.  Another  probable  source  of  error  is  the 
long  drying  on  the  water-bath,  which  may  cause  some  of  the  fatty 
acids  to  become  insoluble  in  petroleum  ether.4 
3Y.  Shimidzu:  Ibid.,  xxviii,  pp.  237-273,  1910. 
4  P.  Hartley:  lour.  Physiol.,  xxxvi,  p.  17,  1909;  xxxviii,  p.  353,  1909.  It 
may  be  mentioned  here  that  Bloor  recently  published  a  new  nephelometric 
method  for  small  amounts  of  fat  in  blood.   This  Journal,  xvii,  p.  377,  1914. 
