558  Assay  of  Citral  in  Lemon  Oil  {XS:..'"?" 
method  being  some  30  per  cent,  higher  in  most  cases.  We  are 
unable  at  present  to  account  for  this,  especially  since  the  same 
sample  of  the  pure  ash  free  active  principle  was  used  as  the  basis 
for  the  determinations  by  the  two  methods.  Apparently  the  most 
plausible  explanation  is  that  referred  to  above,  namely,  that  the 
yellowish  extractive  material  yielded  by  the  samples  is  the  cause  of 
the  lower  readings  by  the  colorimetric  method.  In  spite  of  these 
variations,  however,  we  believe  that  this  test  is  by  far  the  most 
satisfactory  one  at  present  available  and  furnishes  a  means  for 
closely  estimating  the  relative  value  of  different  lots  of  desiccated 
suprarenal  glands  and  i  :  1000  solutions  of  the  active  principle.  We 
hope  to  be  able  in  the  near  future  to  extend  our  experiments  to 
many  other  samples,  both  of  the  desiccated  glands  and  the  com- 
mercial I  to  1000  solutions  and  trust  that  we  will  be  able  to  remedy 
the  cause  of  the  present  differences  in  values  obtained  by  the  two 
methods. 
In  conclusion  special  attention  should  be  called  to  the  very  wide 
differences  in  activity  found  for  the  various  commercial  samples  of 
desiccated  glands  and  the  considerable  diminution  in  strength  of  a 
I  :  1000  solution  of  the  active  principle.  Such  wide  variations  have 
so  far  not  been  reported  for  the  commercial  glands  and  were  not 
expected  when  we  undertook  these  experiments.  They  illustrate 
very  forcibly  the  need  of  just  such  a  simple  method  of  control  of 
this  product  as  is  described  in  the  present  paper. 
ON  THE  PHARMACOPOEIAL  ASSAY  OF  CITRAL  IN 
LEMON  OIL. 
By  J.  R.  RippETOE,  P.D.,  and  Louis  E.  Wise,  Ph.D. 
The  determination  of  Citral  has  for  several  years  past  been 
the  subject  of  considerable  investigation.  In  1906  Chace  ^  proposed 
a  rapid  method  for  the  estimation  of  this  aldehyde,  which  is  appli- 
cable to  the  analysis  of  lemon  oils  and  extracts  and  which  time  has 
shown  to  be  admirably  suited  to  the  needs  and  requirements  of  the 
importer  of  the  essential  oils.  Somewhat  more  recently  Bennet,^ 
modifying  a  method  of  Walther,^  has  suggested  a  means  of  analysis 
'^Journal  of  the  American  Chemical  Society,  28,  1472. 
^Analyst,  34,  1417. 
*  Pharm.  Centr.,  40,  621. 
