48         EXTRACTION  AND  PRESERVATION  OF  AROMATA. 
served  for  an  indefinite  period,  the  following  being  the  mode  of 
operating: — The  elder-flowers  should  be  gathered  when  the 
corolla  is  fully  expanded,  but  not  too  far  gone  ;  they  should 
then  be  plucked  from  the  stem  and  packed  firmly  in  wide-mouth 
bottles  or  jars  without  crushing  them,  and  finally  be  well  covered 
with  glycerine  and  corked.  It  is  not  necessary  that  the  gly- 
cerine should  be  pure  for  this  purpose,  but  it  should  be  devoid 
of  odor  and  have  a  high  gravity  (about  1-240  at  60°  F.).*  The 
common  glycerine  made  from  soap  or  plaster  has  generally  a 
slight  odor,  which  must  be  got  rid  of  before  it  is  used  for  this 
purpose.  When  they  are  wanted  for  the  distillation  of  the 
water,  the  flowers  with  the  glycerine  are  put  into  a  still,  or 
what  is  preferable,  the  glycerine  is  expressed  and  is  then  found 
to  be  saturated  with  the  otto.  Water  is  then  added,  the  quanti- 
ty being  regulated  by  the  original  weight  of  the  preserved  flow- 
ers, or  the  amount  it  is  determined  to  distil.  I  have  preserved 
flowers  for  two  years,  and  on  distilling  them  this  summer  I  have 
procured  a  water,  the  perfume  of  which  equalled  that  made 
from  flowers  of  this  season. 
As  the  essential  oil  seems  soluble  in  all  reasonable  proportions, 
this  is  a  very  convenient  method  of  making  a  concentrated 
water,  either  by  treating  the  glycerine  after  expression  with  a 
fresh  portion  of  flowers  or  by  regulating  the  amount  of  water 
added  on  distillation.  This  process  of  preserving  flowers  will 
be  found  to  far  exceed  the  old  plan  of  preserving  them  between 
layers  of  salt,  particularly  as  it  is  almost  next  to  impossible  to 
distil  the  flowers  so  preserved  without  a  small  portion  of  the 
salt  being  mechanically  carried  over,  which  cannot  be  a  deside- 
ratum in  an  emollient. 
By  diluting  with  water  the  expressed  glycerine,  and  shaking 
it  with  melted  lard,  and  then  allowing  them  to  separate,  an  oint- 
ment may  be  obtained,  which  has  the  natural  properties  and 
aroma  of  the  elder-flowers. 
I  will  now  draw  your  attention  to  what  may  probably  be  a 
very  useful  application  of  the  above  properties  of  glycerine, — 
I  mean  in  cases  where  the  aroma  of  the  flower  is  so  delicate 
*  Pure  distilled  glycerine  has  generally  a  specific  gravity  of  about  1*260 
at  60°  F.,  but  in  ordinary  glycerine  may  be  concentrated  upon  a  water 
bath  until  it  has  a  specific  gravity  of  1*240. 
