Amjuiyri0P9?arm-}     Constants  in  the  Analysis  of  Fats.  377 
dark-colored  oils,  Holde's  method  is  the  best ;  but  with  light-colored 
train  oils,  Morawsky's  process  is  preferable.  As  the  reaction  is  also 
caused  by  colophony  and  shellac,  the  absence  of  these  substances 
must  be  ascertained,  and  should  they  be  present,  it  is  necessary  to 
saponify  the  oil  and  to  test  the  unsaponifiable  portion.  For  dark 
mineral  oils,  it  is  advisable  to  use  an  acid  of  1-53  sp.  gr.,  as  the  use 
of  a  stronger  acid  often  causes  a  dark-yellow  coloration,  which 
renders  the  reaction  less  characteristic.  Samples  of  rosin  oil  exam- 
ined by  the  author  gave  the  reaction  with  this  acid  just  as  plainly 
as  with  the  1-624  SP-  §r-  acid. 
Schadler  remarks  that  train  oil  mixed  with  syrupy  phosphoric 
acid  (5-1)  gives  a  red  color,  which  gradually  turns  very  dark,  and 
is  even  noticed  in  mixtures  containing  only  1  per  cent,  of  the  oil. 
The  author  never  succeeded  in  obtaining  this  reaction,  and  only 
noticed  a  dirty  brown  color.  The  reaction  depends  on  the  nature 
of  the  rosin  oil.  The  author  occasionally  succeeded  in  detecting  an 
admixture  of  5  per  cent.,  but  often  could  not  find  it  at  all.  The 
phosphoric  acid  process  is  therefore  not  to  be  recommended. 
REVISION  OF  CONSTANTS  EMPLOYED  IN  THE 
ANALYSIS  OF  FATS  AND  OILS.1 
By  R.  T.  Thomson  and  H.  Ballantyne. 
In  the  table  of "  constants  in  oil  analysis,"  which  accompanies  the 
original  paper,  will  be  found  collected  that  portion  of  the  authors' 
results  which  they  regard  as  useful  in  oil  analysis. 
Iodine  Absorption. — In  a  previous  communication  {ibid.,  9,  587)  it 
was  shown  that  the  variation  in  iodine  absorption  for  different  olive 
oils  was  greater  than  usually  stated.  Since  then,  it  has  been  found 
to  be  y2  per  cent,  higher  still,  so  that  the  iodine  value  ranges  from 
that  of  Gioja  (79  per  cent.)  to  that  of  Mogadore  olive  oil  (86-9  per 
cent.).  The  lowest  figure  for  rape  oil  now  stands  at  99- 1,  and  the 
highest  at  105-6  per  cent. 
Potash  Neutralizing  Power. — The  figures  respecting  olive  and  rape 
oils  are  in  close  accord  with  those  obtained  by  Archbutt,  and  do  not 
represent  such  a  great  variation  between  each  individual  oil  as  those 
given  by  other  observers.   The  limits  of  five  specimens  of  linseed  oil 
1  J.  Soc.  Chem.  Ind.,  io,  233-237  ;  Jour.  Chem.  Soc,  1892,  547. 
