Am.  Jour.  Pharm.\ 
March,  1896.  J 
Test  for  Gurjun  Balsam. 
143 
the  test  of  experiment.  Accordingly,  the  piate-holder  of  a  Corona 
camera,  whose  slides  are  of  hard  rubber,  and  another  holder  having 
a  pasteboard  slide,  were  taken  for  experiments.  In  one  experiment^ 
two  copper  pennies  and  a  small  brass  key  were  fastened  to  the  sur- 
face of  one  of  the  slides,  beneath  which  was  placed  an  ordinary  dry 
plate,  one  of  Seeds'.  The  margin  of  the  plate-holder  was  covered 
with  black  paper,  to  guard  against  possible  fogging  by  leakage  of 
light,  and  the  holder  was  exposed  for  two  hours  to  direct  sunlight, 
On  development,  there  was  a  very  distinct  shadow  picture  of  the 
pennies  and  key. 
Further  experiments  showed  that  similar  shadow  pictures  could 
be  taken  through  two  thicknesses  of  ordinary  pasteboard,  and 
through  sheets  of  vulcanized  rubber,  i  millimetre  in  thickness, 
but  opaque  to  the  eye.  This  was  accomplished  by  means  o! 
gas  and  kerosene  light,  as  well  as  by  sunlight,  though,  of  course,  in 
these  cases  longer  exposure  was  required  than  when  direct  sunlight 
was  employed.  Various  experiments,  however,  showed  that  the 
rays  did  not  agree  in  their  properties  with  the  X-rays  of  Roentgen, 
They  can  be  reflected  and  refracted,  and  they  penetrate  only  with 
the  greatest  difficulty  a  sheet  of  black  paper.  They  are  probably 
only  the  ordinary  actinic  rays,  which  have  a  power,  heretofore  un- 
suspected, of  penetrating  certain  substances  opaque  to  the  visual 
rays.  The  facts,  however,  are  of  great  practical  importance  to 
manufacturers  and  dealers  in  dry  plates  and  to  those  engaged  in 
the  photographic  art  generally. 
Philadelphia,  February  22,  1896. 
THE  GLACIAL  ACETIC  ACID  TEST  FOR  GURJUN  ~ 
BALSAM  IN  BALSAM  COPAIBA. 
By  Lyman  F.  Kebi^kr. 
In  the  August  number  of  this1  Journal,  I  reported  on  the  effi- 
cacy of  the  above  test.    The  test,  as  outlined  there,  is  a  modification 
of  the  original  one.    In  the  original2  test,  the  balsam  copaiba  is  dis- 
solved in  the  glacial  acetic  acid  and  the  nitric  acid  then  added  to 
the  mixture,  while,  in  the  modification,  the  nitric  acid  is  mixed  with 
the  glacial  acetic  acid,  and  the  balsam  carefully  added  to  this  mix- 
^895,  Am.  Jour.  Pharm.,  c>7,  394. 
2i895,  Am.  Druggist,  27,  5. 
