294 
SPIRITUS  uETHERIS  NITRICI. 
As  the  distillation  proceeds,  the  boiling  mixture  and  the  at- 
mosphere within  the  retort  become  more  yellow  till  the  tempera- 
ture reaches  188°,  and  three  pints  have  passed  over.  The  tem- 
perature then,  if  watched  closely,  will  be  seen  to  fall  from  h°  to 
2°,  according  to  the  amount  of  heat  applied  at  the  time,  and 
coincidently  with  this,  a  material  increase  in  the  rate  of  distilla- 
tion and  color* of  the  distillate  occurs.  This  indicates  the  full 
establishment  of  the  etherifying  reactions,  and  should  be  care- 
fully observed  and  appreciated.  As  soon  as  the  distillation  in- 
creases and  the  temperature  begins  to  fall,  the  heat  should  be 
moderated  down,  and  as  soon  as  the  reaction  is  fully  established, 
the  heat  should  be  entirely  withdrawn.  The  thermometer  then 
falls  very  slowly  and  steadily  to  170°,  the  distillation  also  de- 
creasing till  at  170°  about  5].-  pints  of  distillate  have  passed  over. 
The  heating  is  then  cautiously  resumed,  and  the  thermometer 
kept  steadily  at  or  about  176°  till  65  pints  have  passed  over, 
when  the  process  is  terminated  and  the  apparatus  taken  down, 
thoroughly  rinsed  out,  and  set  up  again. 
The  carbonate  of  potassa  is  added  to  the  distillate  and  well 
shaken  with  it,  the  bottle  being  closed  only  with  the  hand.  The 
mixture  is  then  poured  into  the  retort,  and  the  rectification  com- 
menced, slowly  at  first,  or  at  least  with  a  speed  proportionate 
to  the  capacity  of  the  condenser.  The  mixture  boils  at  about 
80°,  distills  rapidly  at  100°,  and  18  should  pass  over  before 
the  temperature  rises  above  150°.  The  heat  may  then  be  in- 
creased from  time  to  time,  and  the  remainder  pushed  over  rapidly 
till  5j  pints  have  been  received.  The  distillate  is  then  transferred 
to  a  larger  vessel,  alcohol  added  to  it  till  it  measures  17  pints, 
the  whole  well  shaken,  and  then  put  up  in  half  pint  bottles,  well 
filled,  and  well  stopped  with  waxed  glass  stoppers,  and  the  bottles 
covered  -with  dark  blue  paper.  The  whole  process  occupies  about 
4  hours. 
The  product  is  neutral,  of  a  clear  bright  yellow  tint,  and  fra- 
grant odor  free  from  pungency.  The  s.  g.  is  -841  to  -842,  it 
boils  at  156°  to  157p,  and  gives  but  a  pale  straw  color  with  dilute 
solution  of  potassa  within  half  an  hour.  It  is  occasionally  so 
free  from  aldqfayd  that  several  hours  is  required  to  develope  the 
color  with  solution  of  potassa.  The  tint  is  generally  seen  within 
an  hour  by  looking  through  the  test  tube  in  the  direction  of  its 
