174 
Indicators  in  Nature. 
Am.  Jour.  Pharm 
April,  1901. 
Having  been  unable  to  secure  an  oil  of  good  quality,  walnut 
kernels  were  secured,  ground,  and  the  oil  expressed  by  means  of  a 
hydraulic  press.  In  this  way  25  per  cent,  of  oil  was  obtained, 
while  the  kernels  actually  contained  66  per  cent,  of  oil.  It  was 
thus  deemed  of  interest  to  investigate  the  oil,  inasmuch  as  no  such 
examination  seems  to  have  been  made. 
The  oil  generally  used  is  that  obtained  from  Juglans  regia,  L.,  a 
tree  indigenous  to  Persia  and  cultivated  in  Europe  and  America. 
The  kernels  of  this  nut  contain  from  30  per  cent,  to  40  per  cent,  of 
"  virgin "  oil.  The  fresh  cold-drawn  oil1  is  limpid,  nearly  color- 
less or  pale  greenish-yellow  and  of  agreeable  taste  and  odor,  has 
a  specific  gravity  of  0  925  to  0  9265  at  150  C,  saponification  num- 
ber 186-197,  iodine  value  142  to  15  1-7,  fusing  point  of  fatty  acids 
16  to  20°  C,  dries  well  and  is  said  to  be  brought  into  this  country 
from  France  and  Switzerland  in  no- gallon  tuns. 
Hickory  nut  oil  resembles  the  above  walnut  oil  very  much,  and 
is  known  as  "American  Nut  Oil." 
Wm.  T.  Brannt  (1896,  '  A  Practical  Treatise  on  Vegetable  Fats 
and  Oils,"  Vol.  II,  37)  says:  "  Oil  of  black  walnuts  is  sometimes  ex- 
pressed, but  is  of  little  value."  On  examining  the  cold  pressed  black 
walnut  oil,  the  following  physical  and  chemical  constants  were  ob- 
tained :  it  is  limpid,  of  a  straw  yellow  color,  possesses  a  pleasant, 
agreeable,  walnut-like  odor  and  taste,  becomes  turbid  at —  12°  C, 
has  a  specific  gravity  of  09215  at  150  C,  saponification  number 
I90-I-I9r5,  acid  number  8-6-9,  ether  number  181-5-182-5,  Hehner's 
number  93  77,  Reichart-Missel  value  15  c.c,  iodine  value  141-4- 
142-7,  melting  point  of  fatty  acids  0°  C. 
The  drying  qualities  are  excellent,  equal,  if  not  superior,  in 
this  respect,  to  linseed  oil,  leaving  a  tenacious,  flexible,  transparent 
film.  An  artist,  on  using  it,  pronounced  it  a  very  satisfactory  article 
for  fine  painting. 
THE  WIDE  OCCURRENCE  OF  INDICATORS  IN  NATURE.2 
By  G.  S.  Fraps. 
In  the  course  of  some  work  on  a  black  cow-pea  bean,  the  writer's 
attention  was  attracted  by  the  change  from  black  to  red  which  took 
place  when  it  came  in  contact  with  an  acid.    Later,  in  speaking  to 
^'Chemical  Analysis  of  Oils,  Fats,  Waxes,  etc.,"  by  J.  Lewkowitsch,  1898 
P-  35o. 
2Amer.  Chem.  Jour.,  1900,  p.  271. 
