420 
Walnut  Oil. 
/Am.  Jour.  Pharm. 
I      August,  1889. 
marc  left  on  expression  of  the  oil  is  said  to  be  largely  used  in  the 
manufacture  of  chocolate.  Many  people,  I  am  told,  prefer  walnut 
oil  to  olive  oil  for  cooking  purposes. 
The  value  of  this  oil  for  out-door  work  has  been  given  me  by  a 
friend  who  used  it  for  painting  the  verandas  and  jalousies  of  his 
house  (near  Corao,  Italy)  some  twenty  years  ago,  and  which  have  not 
required  painting  since.  In  this  country  at  least,  walnut  oil  is  beyond 
the  reach  of  the  general  painter,  and  I  do  not  know  that  the  pure  oil 
is  to  be  obtained  as  a  commercial  article,  even  on  a  small  scale. 
It  was  in  examining  the  properties  of  this  and  other  oils,  used  as 
adulterants  of  olive  oil,  that  I  was  obliged  to  prepare  them  so  as  to 
be  sure  of  getting  them  in  a  reliable  condition  as  regards  purity.  The 
walnuts  were  harvested  in  the  autumn  of  1887,  and  kept  in  a  dry 
airy  room  uutil  the  following  March.  The  kernels  had  shrunk  and 
contracted  a  disagreeable  acrid  taste,  so  familiar  with  old  olive  oil,  in 
which  this  has  been  used  as  an  adulterant.  Most  oxidized  oils,  espe- 
cially cotton-seed  oil,  reveal  a  similar  acrid  taste,  but  walnut  oil  has, 
in  addition,  an  unmistakable  increase  in  viscosity.  The  nuts  were 
opened  and  the  kernels  thrown  into  warm  water,  so  as  to  loosen  the 
epidermis ;  they  were  then  rubbed  in  a  coarse  towel,  so  as  to  blanch 
them.  The  decorticated  nuts  were  wiped  dry  and  rubbed  to  a  smooth 
paste  in  a  marble  mortar.  The  paste  was  first  digested  in  CS2,  then 
placed  in  a  percolator  and  exhausted  with  the  same  solvent,  which 
was  evaporated  off.  The  yield  of  oil  was  small,  but  probably,  if  the 
nuts  had  been  left  to  fully  ripen  on  the  trees  without  knocking  them 
off  the  yield  might  have  been  greater.  It  is  by  no  means  improbable 
that  oxidation  may  have  rendered  a  portion  of  the  oil  insoluble.  The 
decorticated  kernels  gave  a  perfectly  sweet,  inodorous,  and  almost 
colorless  oil,  which  rapidly  thickens  to  an  almost  colorless,  transpar- 
ent, and  perfectly  elastic  skin  or  film,  which  does  not  darken  or  crack 
easily  by  age.  These  are  properties  which  for  fine  art  painting,  might 
be  of  great  value  in  preserving  the  tinctorial  purity  and  freshness  of 
pigments. 
Sulphur  chloride  gives  a  perfectly  white  product  wtth  the  fresh  oil, 
but,  when  oxidized,  the  product  is  very  dark,  almost  black.  The 
iodine  absorption  of  the  fresh  oil  thus  obtained  is  very  high,  but  falls 
rapidly  by  oxidation  or  blowing.  A  curious  fact  has  been  disclosed 
with  reference  to  the  oxidation  of  this  and  similar  oil's.  If  such  an 
oil  be  mixed  with  lard  oil,  olive  oil,  or  sperm  oil,  it  thickens  by  oxida- 
