234  Adulteration  of  Castor  and  Olive  Oils.  {^'^iS®™- 
The  observation  of  the  rise  of  temperature  with  sulphuric  acid  is 
a  most  important  factor,  and  may  be  considered  to  be,  if  not  the 
most  important,  one  of  the  most  valuable  tests  of  those  used  to 
ascertain  the  genuineness  or  otherwise  of  the  olive  oil  submitted  for 
analysis.  Pure  olive  oil,  according  to  many  observers,  giVes  390  to 
440  ;  our  own  experiments  with  the  pure  oil  gave  400  to  430.  The 
usual  adulterants  of  olive  oil  give  much  higher  figures  than  these. 
We  found  the  elaidin  test  of  little  value,  except,  of  course,  in  indi- 
cating that  the  samples  were  sophisticated  ;  for  identification  of  the 
adulterant  our  results  were  not  such  as  would  allow  us  to  pass  an 
opinion  as  to  the  oil  used  for  mixing  with  the  olive  oil. 
The  behavior  of  the  samples  of  oil  with  glacial  acetic  acid  (E. 
Valenta,  Dingl.  polyt.  J.,  cclii,  296;  J  oar.  Chem.  Soc.,  xlvi,  1078) 
was  observed.  Equal  parts  of  the  oil  and  glacial  acetic  acid  were 
mixed  and  gently  heated,  with  shaking,  until  the  oil  dissolved  in 
the  acetic  acid.  Our  observations  gave  for  the  pure  samples  we 
examined  95 0  C,  whilst  our  figures  for  the  oils  suspected  of  not 
being  genuine  were  very  much  lower  in  every  case.  The  import- 
ance of  this  test  can  only  be  appreciated  after  long  and  careful 
trial. 
We  also  used  Hubl's  iodine  absorption  method.  For  pure  olive 
oil  Hiibl  gives  816  to  84.  Our  own  experiments  gave  81  o  to  84-5 
for  the  pure  oil.  The  figures  obtained  from  the  oils  commonly  used 
as  adulterants  are  much  higher  than  this,  as  were  the  figures  we 
obtained  from  our  samples. 
Tabi,k  II. 
Specific 
Gravity. 
Rise  of 
Tempera- 
ture. 
Iodine 
Absorption. 
Saponifica- 
tion Equiv- 
alent. 
Valenta. 
I,  .... 
•9199 
6o°  C. 
100 -o 
288 
68°  C. 
2,  .... 
•9182 
6o°  C. 
97-5 
288 
6o°  C. 
3,    •  • 
•9186 
6o°  C. 
93  'o 
286 
55°  C. 
4,    .  .  .  . 
•9194 
55°  C 
57°  C. 
93-5 
293 
55°  C. 
5  
•9190 
99  0 
297 
50°  c. 
6,  .... 
•9187 
650  c. 
640  c. 
66°  C. 
96*5 
288 
58°  c. 
55°  C. 
7,  .... 
•9187 
97  0 
288 
8,  .... 
•9188 
96-0 
290 
55°  C. 
9,  .... 
•9187 
640  C. 
97"5 
290 
500  c. 
10,  .... 
•9188 
68°  C. 
96-5 
288 
54°  C. 
11,       .  .  . 
Pure  oil,  .  . 
•9187 
670  C. 
97 '5 
289 
52°  C. 
•9170 
4o-43°  c. 
81-84-5 
285-296 
95°  C. 
