104  Alcohol  in  Concentrated  Nitrous  Ether.       { Amiil™hjm*m' 
ent  into  acetic  acid.  Potassium  permanganate,  either  solid  or  in 
solution,  may  be  added  to  destroy  the  nitrous  ether  and  has  the 
advantage  of  roughly  showing  the  amount  of  nitrous  ether  present. 
Potassium  iodide  with  sulphuric  acid  cannot  be  used  to  destroy  the 
nitrous  ether,  owing  to  later  volatilization  of  the  iodine. 
It  is  well  to  titrate  a  portion  with  tenth  normal  potassium  per- 
manganate, to  form  an  idea  of  the  amount  of  nitrous  ether  present. 
I  prefer  to  do  this  and  then  use  sufficient  chromic  acid  mixture  to 
both  destroy  the  nitrous  ether  and  convert  the  alcohol,  as  potassium 
permanganate  leaves  a  muddy  residue.  One  or  two  trials  may  be 
necessary  to  determine  the  exact  quantity  to  be  used.  After  the 
addition  of  the  chromic  acid,  the  bottle  is  firmly  closed  and  heated  for 
two  hours  in  a  steam-bath  at  ioo°  C.  At  the  end  of  this  time  the 
solution  should  not  be  green,  but  should  have  a  small  excess  of 
chromic  acid.  The  bottle  must  now  be  cooled  to  room  temperature, 
opened,  and  a  small  piece  of  metallic  zinc  added  to  destroy  the  excess 
of  chromic  acid  ;  when  solution  is  green,  it  is  poured  into  a  distilling 
flask,  the  bottle  washed  into  same  flask  and  carefully  distilled,  using 
a  well-cooled  condenser.  When  liquid  in  distilling  flask  is  nearly 
to  dryness,  add  more  water  and  again  distil  almost  to  dryness.  It 
last  few  drops  of  distillate  are  acid  to  litmus  paper,  again  refill  and 
distil.  Test  distillate  with  a  drop  of  barium  chloride  solution  to  be 
positive  no  sulphuric  acid  has  been  carried  over,  and  titrate  with 
standard  alkali  and  compute  alcohol  present  in  original  sample. 
ANALYTICAL  RESULTS. 
Using  flask  connected  with  thistle  tube  and  air-cooled  glass  spiral, 
the  following  results  were  obtained : 
No.  Per  cent. 
1.  Using  KI  and  H2S04  to  destroy  nitrous  ether  present,  alcohol  indicated  6'n 
2.  "     KMnO,  "     "  w        "  "  "  "  1173 
3.  "     chromic  acid     "     "  "        "  "  "  "  H'53 
4.  "  "       "        "     "  "        "  "         "  "  15*30 
5.  "  "       "        "     "  "        "  "  "  "  15-02 
Using  series  of  five  wash-bottles  with  different  amounts  of  dilute 
alcohol  and  chromic  acid  and  on  different  days,  the  following  results 
were  obtained : 
