328  PREPARATION  OF  SPIRIT  OF  NITROUS  ETHER. 
well  for  the  purpose  for  which  it  was  intended,  and  it  was  in 
working  with  this  process  and  making  some  modifications  in  it, 
that  I  discovered  one  which  appears  to  present  advantages  over 
any  other  process  I  know  for  the  preparation  of  spirit  of  nitrous 
ether.  There  appeared  to  he  some  difficulty  in  adopting  even  a 
modification  of  Kopp's  process  on  account  of  the  increased  con- 
sumption of  nitric  acid  which  it  involved  and  the  cost  of  the 
copper  consumed  in  the  process,  for  the  nitrate  of  copper  that 
would  be  formed,  if  the  process  were  generally  used  in  a  manu- 
facture of  this  extent,  would  not  be  likely  to  find  a  market. 
Other  substances,  acting  in  the  same  direction  as  the  copper,  for 
deoxidizing  the  nitric  acid,  were  tried,  but  without  much  success. 
I  am  informed  that  manufacturers  sometimes  use  iron  as  well  as 
copper  stills  in  making  sweet  spirit  of  nitre,  and  thus  get  better 
results  than  are  obtained  when  the  distillation  is  effected  in  glass 
or  stoneware ;  but  in  my  experiments  I  have  not  obtained  any 
satisfactory  results  by  the  use  of  iron.  Several  experiments 
were  made  with  starch,  and  also  with  sugar  and  glycerine.  Many 
years  ago,  in  1850,  Mr.  Grant,  of  Bristol,  suggested  the  use  of 
starch  instead  of  copper  in  Kopp's  process  ;  but  in  attempting 
to  apply  it  in  the  preparation  of  spirit  of  nitrous  ether,  with  an 
increased  quantity  of  spirit  in  contact  with  the  nitric  acid,  I 
have  found  that  the  starch  remains  undissolved  and  unaltered  in 
the  mixture  of  spirit  and  acid  until  so  much  spirit  has  been  dis- 
tilled off  as  to  leave  the  nitric  acid  with  about  four  times  its 
volume  of  spirit,  when  nitrous  ether  begins  to  be  formed.  This, 
however,  is  just  the  point  at  which  the  ether  would  be  formed  if 
there  was  no  starch  present.  The  starch  certainly  acts  bene- 
ficially in  one  respect, — its  particles  diffused  through  the  mixture 
of  acid  and  spirit  cause  the  liquid  to  boil  more  freely  and  regu- 
larly than  it  otherwise  would,  and  the  temperature  is  therefore 
less  subject  to  variation  than  it  is  in  the  distillation  of  the  acid 
and  spirit  alone.  When  the  formation  of  ether  has  commenced 
the  process  proceeds  satisfactorily  for  some  time,  but  at  last  a 
very  violent  reaction  takes  place,  and  nitrous  fumes  are  copiously 
evolved,  which,  if  allowed  to  pass  into  the  distillate,  would  render 
the  product  unfit  for  use. 
As  the  starch  remains  in  an  insoluble  state  in  the  mixture  until 
