562 
then  contains 
Assay  of  Citral  in  Lemon  Oil.        { ^Dc'ceXV 
X  25  or  3.46  mgs.  of  Citral. 
Pbarm. 
1911. 
1.2x3  1 
In  other  words  3.2  c.c.  of  the  original  solution  of  oil  of  lemon 
contain  3.46  mgs.  of  Citral  and  ^.2  c.c.  of  this  same  solution  also 
contain  8^.2  mgm.  of  oil  ^— 
Then 
3.46  mgm.  Citral 
300     3.2  100 
  X  X 
50         I  I 
83 
■■) 
X  100  =  Percentage  Citral  in  the  oil 
83.2  mgm.  of  oil 
=  4.16  per  cent. 
It  may  be  of  interest  tO'  note  the  close  readings  which  can  be 
obtained  by  the  metaphenylene  diamine  method.  They  are  shown 
in  Table  I. 
Table  I. 
Sample  number 
Per  cent,  citral  (Hiltner's  Method) 
Ila 
3.88;  3.89. 
Tib 
4.19;  4.22;  4.07. 
9469 
4.05;  3.89. 
9427 
4. 1 1 ;  4. 1 1. 
Table  II  shows  the  Citral  content  of  the  oils  as  determined  by 
the  three  methods. 
Table  II. 
Sample  number 
By  U.S. P.  Method 
By  Chace's  Method 
By  Hiltner's  Method 
II 
9469 
9427 
4.17  per  cent. 
4.44  per  cent. 
4.30  per  cent. 
4.04  per  cent. 
4.20  per  cent. 
4.50  per  cent. 
4.35  per  cent. 
4.16  per  cent. 
3.89  per  cent. 
3.97  per  cent. 
4.1 1  per  cent. 
As  a  result  of  this  limited  investigation,  we  beg  to  recommend 
that  the  Hiltner  method  be  further  studied,  and  that  if  possible,  it 
be  substituted  for  the  pharmacopoeial  sulphite  method  now  in  use. 
The  former  is  apparently  more  accurate  (since  it  does  not  deter- 
mine the  Citronellal  and  thus  introduce  a  positive  error)  and  is  un- 
doubtedly much  more  rapid  and  far  less  troublesome.  The  results 
obtained  may  naturally  be  somewhat  lower  and  if  the  method  is 
adopted  it  may  be  found  necessary  to  change  the  U.  S.  P.  require- 
ments from  4  per  cent,  to  approximately  3.8  per  cent,  of  Citral. 
Research  Department, 
ScHiEFFELiN  &  Co.,  Ncw  York. 
November  i,  191 1. 
