SPIRITUS  iETHEEIS  NITRICI. 
291 
with  safety  to  the  product,  and  as  very  little  ether  is  formed  at 
the  close  of  the  process,  it  is  better  to  arrest  it  an  ounce  or  two 
short  of  the  prescribed  volume,  than  to  risk  a  higher  temperature. 
If  carefully  managed,  it  is  easy  to  control  or  arrest  the  process 
at  any  stage,  by  diminishing  or  stopping  off'  the  heat ;  but  if  in- 
cautiously managed,  a  new  and  comparatively  uncontrollable  re- 
action occurs,  which  produces  no  ether,  but  aldehyd  and  hydro- 
cyanic acid  vapors  in  abundance.  The  operator  should  therefore 
be  always  in  readiness  to  remove  the  receiving  bottle,  particular- 
ly if  using  larger  quantities  of  materials  than  those  of  the 
officinal  formula.  At  the  end  of  the  process  the  retort  contains 
36  f.5  of  residue,  in  two  layers.  The  upper  one,  of  say  4  to  6 
f.5,  is  yellow,  transparent  and  oleaginous  ;  the  lower  is  white  or 
opaque  from  mechanical  admixture  of  an  undissolved  salt.  This 
residue  should  be  poured  at  once  from  the  retort,  in  order  to 
avoid  risk  of  losing  the  vessel  in  the  attempt  to  get  it  out  after 
it  solidifies.  This  residue  boils  actively  long  after  being  poured 
into  a  cool  vessel,  and  the  vapors  given  off  by  it  are  hurtful. 
The  retort,  condenser,  and  all  the  muslin,  &c,  used  about  the 
connections  having  been  thoroughly  washed,  and  the  apparatus 
again  set  up,  the  rectification  is  commenced. 
The  carbonate  of  potassa  having  been  put  into  the  receiving 
bottle  at  the  commencement  of  the  process,  and  the  distillate 
having  been  received  upon  it,  the  whole  is  now  well  shaken  up 
with  the  palm  of  the  hand,  only,  over  the  bottle  mouth,  and  poured 
into  the  cleansed  retort,  and  the  bottle  rinsed  in  with  the  diluted 
alcohol.  The  bottle  is  then  rinsed  clean,  tied  over  as  before,  and 
replaced  in  the  apparatus,  when  the  heating  is  cautiously  resumed. 
At  130°  to  133°  the  liquid  will  fairly  boil,  and  must  be  kept  from 
boiling  too  rapidly  for  the  capacity  of  the  condenser,  as  it  is  easy 
to  drive  off  an  important  portion  of  the  ether  by  too  rapid  heat- 
ing at  first.  One  fourth  of  the  gallon  should  pass  over  before 
the  temperature  rises  above  176°,  and  as  this  portion  contains 
nearly  all  the  ether,  the  remainder  being  more  easily  condensed 
may  be  distilled  more  rapidly. 
If  the  first  fourth  of  this  distillate  be  kept  apart  and  distilled 
fractionally,  it  commences  to  boil  at  68  to  72°,  boils  rapidly  and 
distils  fast  at  74°,  and  then  steadily  and  more  and  more  slowly 
arises  to  156°.    The  receiver  is  then  changed  and  8  f.3  more 
