OLEUM  JETHEREUM  AND  SPIRITUS  J3THERIS  COMPOSITUS.  197 
that  washing  with  solution  of  potassa  of  the  prescribed  strength 
decomposed  some  of  the  oil,  or  rendered  it  soluble  to  a  certain 
extent. 
It  was  next  noticed  that  the  fuller  the  retort  the  larger  the 
yield ;  and  this  is  probably  due  to  the  fact  that  the  oil  must  be 
mechanically  carried  over  with  the  vapors  from  being  produced 
and  distilled  at  a  temperature  much  below  its  boiling  point.  A 
shallow  leaden  still  would  doubtless  give  a  larger  product. 
The  accurate  management  and  regulation  of  the  fire  and  tem- 
perature by  an  immersed  thermometer,  was  the  next  step  attain- 
ed ;  and  finally,  it  was  observed  that  when  the  sulphate  of  lead 
precipitated  from  the  acid  on  dilution,  was  suffered  to  separate 
completely,  and  was  carefully  excluded  from  the  retort,  the  yield 
was  at  least  one-third  greater.  Indeed,  such  an  influence  has 
this  small  precipitate  upon  the  viscosity  of  the  boiling  mixture 
toward  the  close  of  the  process,  that  when  excluded,  and  the 
temperature  carefully  managed  no  frothing  up  occurs,  and  the 
boiling  can  be  continued  until  only  uncondensable  gases  pass 
over.  This  is  the  most  important  fact  yet  arrived  at  in  connec- 
tion with  this  process. 
The  formula  now  used  is  as  follows : 
Take  of  Alcohol,  (s.  g.  -835,)        1  gal.=  6  ft).  12  oz.  av. 
Sulphuric  acid,  (s.-g.  1-845)  lga!.14|fj  =16ft>.  14oz.  av. 
Carbonate  of  soda,  10  grs. 
Distilled  water,  a  sufficient  quantity. 
To  the  alcohol,  in  a  suitable  vessel,  add  the  sulphuric  acid 
slowly.  Stir  the  mixture  and  allow  it  to  stand  twenty-four  hours. 
Decant  the  clear  liquid  into  a  three  gallon  retort,  excluding  all 
the  sediment,  and  distil  it  from  a  sand  bath  at  a  temperature 
between  318°  and  330°,  till  a  black  froth  arises  in  the  retort,  or 
until  the  distillation  of  liquid  ceases,  and  only  gaseous  pro- 
ducts pass  through  the  condenser.  Separate  the  oily  stratum 
from  the  distillate,  and  expose  it  for  twelve  hours  in  a  shallow 
capsule.  Wash  it  first  with  an  equal  volume  of  distilled  water, 
then  with  a  solution  of  the  carbonate  of  soda  in  a  similar  pro- 
portion of  distilled  water,  and  finally  with  distilled  water  again. 
The  finished  product  should  measure  at  least  ten  fluid  drachms, 
S.  g.  1.1. 
On  mixing  the  alcohol  and  acid  the  mixture  becomes  heated 
