278  Andalusian  Essential  Oils.         {Am-Ap°rf  ig*8.m' 
der  season  the  Sociedad  Santiago  sends  a  small  steam  still,  with  a 
capacity  of  100  gallons,  operated  by  a  traction  engine,  into  the 
country. 
The  prices  paid  for  the  various  plants  and  berries  to  be  used  for 
distillation  vary  considerably.  The  present  price  of  most  of  them 
ranges  from  1.20  to  1.80  pesetas  per  100  pounds  delivered  at  the 
place  of  distillation.  Cultivated  herbs,  such  as  the  geranium,  bring 
a  higher  price.   Juniper  berries  cost  12  pesetas  per  100  pounds. 
The  Process  of  Manufacture. — In  Andalusia  the  aromatic  plants 
are  not  dried  before  distillation,  but  are  used  as  they  come  from  the 
country.  They  are  placed  in  the  distillery  vats ;  steam  is  then  intro- 
duced from  the  botton,  so  that  it  diffuses  evenly  and  forces  upward 
through  the  plants ;  the  heat  of  the  steam  expands  the  globules  of 
oil  which  are  contained  in  the  minute  cells  of  the  leaves,  causing 
them  to  burst.  The  oil  thus  freed  is  carried  off  in  the  current  of 
steam.  The  steam  charged  with  the  essential  oil,  having  passed 
through  the  plants  to  the  top  of  the  vat,  escapes  through  a  valve 
to  the  primary  condenser,  which  consists  of  a  serpentine  copper 
coil  over  which  cold  water  flows.  The  distillate  after  traversing 
this  worm  falls  into  a  receiver  having  an  exterior  pipe  leading  from 
the  bottom  to  a  height  nearly  equal  to  that  of  the  receptacle.  As 
the  distillate  flows  into  the  receiver,  the  water,  being  heavier  than 
the  oil,  sinks  to  the  bottom  of  the  vessel  and  is  forced  out  through 
the  discharge  pipe. 
In  some  countries  this  water,  which  does  not  throw  off  the  entire 
amount  of  essential  oil  contained,  is  returned  to  the  boiler  and  re- 
converted into  steam  and  continuously  used.  This  system  is  em- 
ployed in  the  Malaga  district  only  in  the  preparation  of  rose  oil. 
The  essential  oil  collects  upon  the  top  until  the  tank  is  filled.  The 
whole  process  takes  about  three  hours.  As  thus  distilled  from  the 
plants  the  product  obtained  is  the  natural  oil,  which  always  contain 
an  insoluble  resin.    It  is  in  this  form  that  the  oil  is  usually  sold. 
Vacuum  System  of  Refining  Used. — Prices. — To  give  the  oil  the 
greatest  possible  concentration,  aroma,  and  solubility  and  to  free  it 
from  foreign  substances,  it  is  treated  by  the  vacuum  process.  The 
old  style  was  to  repeat  the  process  of  distillation  described  above. 
The  newer  vacuum  system  is  much  superior  because  the  oil  boils  at 
a  much  lower  temperature,  which  prevents-  the  decomposition  of  the 
oil.  The  system  employed  is  identical  with  the  first  distillation  ex- 
cept that  the  natural  oil  instead  of  the  plant  is  placed  in  the  vat  for 
