378 
Constants  in  the  Analysis  of  Fats. 
/  Am.  Jour.  Pharra. 
I        July,  1892. 
examined  by  the  authors  vary  from  19-00  to  19-28,  whilst  those  of 
nine  specimens  tested  by  other  observers  and  recorded  by  Allen 
range  between  18-74  anQl  T9-52- 
Unsaponifiable  Matter.  —  Olive,  refined  cotton-seed,  unrefined 
arachis,  and  linseed  oils,  contain  about  the  same  proportion  of 
unsaponifiable  matter,  so  that  the  determination  of  that  constituent  in 
a  sample,  say  of  olive  oil,  would  not  serve  to  show  any  adulteration 
with  either  of  the  other  three  oils  But  the  presence  of  a  consider- 
able portion  of  rape  oil  would  tend  to  reduce  the  percentage  of 
unsaponifiable  matter.  In  marine  oils,  it  is  noteworthy  that  seal 
oils  contain  only  about  one-third  of  that  contained  in  whale,  cod 
and  menhaden  oils. 
Specific  Temperature  Reaction. — This  is  merely  a  modification  in 
recording  the  results  of  Maumene's  reaction  with  strong  sulphuric 
acid.  It  consists  in  mixing  50  grams  of  water  with  10  cc.  of  sul- 
phuric acid,  each  at  200,  and  registering  the  highest  temperature 
reached.  The  amount  of  water  is  best  measured  from  a  pipette  at 
15  50,  and  the  sulphuric  acid  should  be  run  in  from  a  pipette  which 
will  deliver  the  10  cc.  in  one  minute.  During  the  addition,  the 
mixture  should  be  vigorously  stirred  with  the  thermometer,  and  the 
highest  temperature  reached  rapidly  read  off,  as  it  only  remains 
constant  for  a  few  seconds.  The  oil  being  tested  in  precisely  the 
same  manner,  it  is  only  necessary  to  divide  the  rise  in  temperature 
obtained  with  water  into  that  obtained  by  the  oil  under  examina- 
tion. The  answer  is  the  specific  temperature  reaction  compared 
with  water  as  100.  The  oils  must  be  carefully  weighed,  and  the 
acid  added  to  them  exactly  as  with  water,  except  that  even  more 
vigorous  stirring  is  necessary  during  and  after  the  addition  of  acid. 
In  this  way,  the  rise  in  temperature  in  all  the  experiments  made  by 
the  authors  was  fairly  steady  up  to  the  highest  point,  at  which  the 
temperature  remained  constant  for  50  to  60  seconds.  In  the  case 
of  linseed,  cod,  seal  and  menhaden  oils,  the  tests  had  to  be  made 
with  a  mixture  of  20  grams  of  these  oils  and  30  grams  of  olive  oil 
of  known  specific  temperature  reaction.  As  a  rule,  an  oil  having  a 
high  iodine  absorption  has  also  a  high  specific  temperature  reaction, 
but  the  rise  is  not  always  directly  as  that  in  the  former.  The  reason 
the  specific  temperature  reaction  cannot  be  depended  on  with  the 
same  assurance  as  the  iodine  value  is  that  it  shows,  in  some  cases, 
large  variations  for  the  same  class  of  oils. 
