420  Characteristics  of  Olive  Oil. 
ble  albuminate  is  one  of  the  phenomena  which  takes  place  during  the 
formation  of  gluten. 
The  second  class  of  vegetable  globulins,  the  paraglobulins,  is  in  dis- 
tinct contrast  with  that  of  the  myosins.  Two  protei'ds  of  this  class 
have  been  found,  one  in  papaw  juice,  the  other  in  the  seeds  of  Abrus 
precatorius  (jequirity).  Both  these  globulins  exhibit  the  following 
properties  :  they  are  soluble  in  saline  solutions,  and  are  precipitated  by 
saturation  with  sodium  chloride  and  magnetium  sulphate.  In  a  10 
per  cent,  solution  of  magnesium  sulphate,  they  coagulate  betweeu  70° 
and  75°.  When  precipitated  from  their  saline  solutions  by  dialysis, 
they  are  still  soluble  in  solutions  of  sodium  chloride  and  magnesium 
sulphate  of  10 — 15  per  cent.,  not  being  transformed  into  albuminates. 
Nor  are  they  precipitated  by  long  exposure  (over  three  days)  to  a 
temperature  of  35 — 40°. 
CHARACTERISTICS  OF  OLIVE  OIL. 
A.  Levallois  (Compt.  rend.,  civ,  371 — 373),  has  examined  a  large 
number  of  genuine  samples  of  olive  oil  from  the  olive  yards  of  the 
south-east  of  France. 
The  color  of  the  oil  was  determined  by  means  of  a  Duboscq  color- 
imeter. The  color  at  the  commencement  of  a  crop  is  70  times  as  in- 
tense as  at  the  end.  The  sp.  gr.  at  15°  varies  from  0*9167  to  0*9177, 
and  the  differences  observed  with  different  species  are  only  very  slight. 
The  sp.  gr.  of  olive  oil  at  24°  is  0*911,  whilst  that  of  other  oils  at  the 
same  temperature  is  as  follows  : — 
Sesame   0*917  Colza   0*910 
Cotton-seed  0*9165  Camelina   0-920 
Earth-nut  0*912  Linseed  0-928 
Poppy   0  9205 
The  sp.  gr.  of  colza  and  earth-nut  oil  are  somewhat  near  that  of 
olive,  but  their  other  properties  make  it  easy  to  distinguish  be- 
tween them. 
Cailletet's  reagent  (nitric  acid  saturated  with  nitrogen  oxides)  usual- 
ly gives  a  green  coloration,  which,  however,  is  not  always  pure,  but  is 
sometimes  mixed  with  yellow. 
Audoynaud's  reaction  (addition  of  nitrosulphuric  acid  and  ether  to 
a  mixture  of  the  oil  with  potassium  dichromate)  usually  gives  a  green 
coloration,  which  in  some  cases  is  mixed  with  yellow. 
