PREPARATION  OF  SPIRIT  OF  NITROUS  ETHER. 
32T 
or  (3)  by  interposing  an  inert  medium  between  the  acid  and 
alcohol,  through  which  they  shall  mutually  pass  by  diffusion ;  or 
(4)  by  causing  the  nitric  acid  to  be  gradually  produced  in  the 
retort  by  the  decomposition  of  a  nitrate  ;  or  (5)  by  substituting 
a  nitrite  for  a  nitrate ;  or  (6)  by  substituting  nitrous  acid  for 
nitric  acid  in  the  free  state  ;  or  (7)  by  using  some  ingredient 
which,  in  the  presence  of  the  spirit,  will  convert  the  nitric  into 
nitrous  acid,  without  involving  the  destruction  of  alcohol  and 
consequent  formation  of  aldehyd  and  other  secondary  products. 
The  processes  of  the  Edinburgh  and  Dublin  Pharmacopoeias 
belong  to  methods  (1)  and  (2) ;  they  can  only  be  practically 
applied  on  the  small  scale,  and  they  are  not  economical.  The 
process  referred  to  under  (3)  is  that  of  Dr.  Black,  which  Berze- 
lius  preferred  to  all  the  others  ;  but  this,  again,  is  not  a  manu- 
facturer's process,  and  cannot  be  made  such.  It  consists  in 
putting  into  a  long  narrow  cylindrical  vessel  9  parts  of  rectified 
spirit,  then  introducing  beneath  this,  by  means  of  a  funnel-tube 
reaching  to  the  bottom  of  the  vessel,  4  parts  of  water,  so  that  it 
shall  form  a  distinct  stratum  beneath  the  spirit,  and  afterwards 
introducing  in  the  same  way,  beneath  the  water,  8  parts  of  strong 
nitric  acid.  These  are  allowed  to  stand  undisturbed,  for  two  or 
three  days,  in  a  room  at  a  uniform  temperature,  not  exceeding 
53°.  At  the  ei.d  of  the  process,  when  carefully  conducted,  a 
stratum  of  nitrous  ether  is  found  floating  over  an  acid  liquor. 
The  method  referred  to  under  (4)  presents  no  advantage  over  (1) 
and  (2) ;  (5)  is  the  process  of  the  British  Pharmacopoeia  of  1864  ; 
and  (6)  is  Liebig's  process,  which,  although  presenting  some  ad- 
vantages, is  liable  to  become  unmanageable  when  anything  more 
than  small  quantities  are  operated  upon,  and  is,  in  other  respects, 
unsuited  for  operations  on  a  large  scale.  The  last  of  the  methods 
referred  to  (7),  appeared  to  me  to  present  the  greatest  proba- 
bility that  a  process  might  be  founded  upon  it  capable  of  accom- 
plishing what  is  required. 
Kopp's  procoss  for  the  production  of  nitrous  ether,  consists  in 
heating  a  mixture  of  equal  volumes  of  rectified  spirit  and  nitric 
acid,  sp.  gr.  1-36,  in  contact  with  copper  filings,  and,  when 
chemical  action  has  commenced,  withdrawing  the  heat  and  allow- 
ing the  distillation  to  go  on  spontaneously.  This  process  answers 
