376 
Detection  of  Rosin  Oil. 
/  Am.  Jour.  Pharm. 
t        July,  1892. 
is  to  be  taken ;  the  short  tube  is  then  connected  with  a  water  aspi- 
rator. The  advantages  of  this  process  consist  in  the  comparatively 
short  time  required  for  solution,  and  in  the  circumstance  that  no 
expensive  apparatus,  such  as  water  motors  and  revolving  agitators, 
are  required.  In  places  where  high-pressure  water  is  not  available, 
steam  may  be  substituted  by  attaching  a  flask  of  boiling  water  to 
the  aspirator.  The  objections  to  the  process  are  that  the  solution 
may  be  supersaturated  by  the  air  causing  evaporation  during  its 
passage  through  the  liquid  ;  and,  secondly,  that  readily  oxidizable 
substances  cannot  be  examined  in  this  way.  The  first  objection 
may  be  overcome  by  the  use  of  moist  air,  whilst  the  second  diffi- 
culty can  usually  be  met  by  employing  coal  gas  in  place  of  air,  care 
being  taken  that  the  oxygen  and  carbonic  anhydride  present  in  the 
gas  are  thoroughly  absorbed  by  alkaline  pyrogallol  solution. 
DETECTION    OF   ROSIN    OIL    IN   FATTY  AND 
MINERAL  OILS.1 
By  A.  Grittner. 
The  original  process  proposed  by  Storch  has  only  a  limited  appli- 
cation, as,  when  sulphuric  acid  is  added  to  the  solution  of  the  oil  in 
acetic  anhydride,  train  oil  gives  a  red  color,  whilst  with  cholesterol, 
present  in  many  fatty  oils,  a  violet  one  is  produced.  With  dark- 
colored  mineral  oils,  the  process  fails  altogether.  Morawsky  has 
modified  the  process  by  using  a  weaker  acid  of  1-53  sp.  gr.  Holde 
also  made  use  of  this  acid  (without  the  acetic),  but  of  late,  he  has 
increased  the  strength  to  1-624  sp.  gr.,  as  with  the  weaker  acid  the 
violet-red  color  takes  a  long  time  to  develop.  The  author  found 
that  when  mixing  rape  oil  with  1  per  cent,  of  rosin  oil,  the  adultera- 
tion may  be  easily  detected  by  Holde's  original  or  modified  process  ; 
but  Morawsky's  method  was  still  more  delicate  ;  as  it  showed  y2 
per  cent.  Black  rosin  oil  did  not  give  such  a  characteristic  reaction 
as  was  observed  with  oils  of  a  lighter  color.  Train  oils,  before  being 
tested,  must  be  shaken  with  alcohol,  and  the  alcoholic  solution 
tested  for  the  rosin  oil.  The  reaction  is  best  observed  by  allowing 
sulphuric  acid  to  run  down  the  side  of  the  test  tube;  if  rosin  oil  be 
present,  a  red  or  violet  ring  will  form  at  the  point  of  contact.  With 
1  Zeit.  ang.  Chem.,  1892,  265;  Jour.  Chem.  Soc,  1892,  p.  548. 
