AmjSeri8P98arm'}     Amyl  Nitrite  and  Nitrous  Ether.  275 
have  prevented  this  modification  from  becoming  popular.  D. 
Walker  [Am.  Drug.,  1896^.79)  reported  results  agreeing  fairly  well 
with  others  obtained  by  nitrometer,  through  substitution  of  acetic 
for  sulphuric  acid  in  Dott's  method  and  without  precautions  to 
exclude  air.  L.  A.  Kessler  (Am.  Jour.  Phar.,  1897,  p.  307)  found 
this  unsatisfactory  because  of  liability  of  giving  too  high  results. 
The  conflicting  statements  regarding  this  method  in  its  various 
modifications  induced  the  writer  to  make  some  experiments  to  deter- 
mine if  it  could  not  in  some  way  be  adapted  to  the  use  of  the  phar- 
macist for  approximate  estimations. 
When  spirit  of  nitrous  ether,  solution  of  potassium  iodide  and 
dilute  sulphuric  acid  were  mixed  in  a  flask  with  access  of  air,  in  the 
same  proportions  as  in  the  gasometric  method,  the  quantity  of 
iodine  liberated  in  a  few  moments  would  be  two  or  three  times  as 
much  as  was  required  by  the  nitrite  present ;  when  the  spirit  was 
diluted  with  water  before  admixture  with  the  reagents,  the  libera- 
tion of  the  iodine  was  slower,  but  also  greatly  in  excess  of  the  theo- 
retically required  amount,  and,  after  decoloration,  the  solution  would 
rapidly  become  brown  again  from  further  liberation  of  iodine. 
When  access  of  air  was  prevented  by  a  layer  of  liquid  paraffin  on 
the  surface,  the  reaction  was  not  complete  in  any  reasonable  time, 
only  one-half  to  two-thirds  of  the  actual  amount  of  nitrite  being  indi- 
cated. At  the  same  time  a  portion  of  the  iodine  dissolved  in  the 
paraffin,  thus  in  part  escaping  titration. 
Dott's  later  method  consists  in  mixing  10  c.c.  each  of  a  10  per 
cent,  solution  of  potassium  iodide,  of  a  15  per  cent,  solution  of  potas- 
sium bicarbonate,  of  rectified  spirit  and  5  c.c.  of  spirit  of  nitrous 
ether,  then  adding  10  c.c.  of  dilute  sulphuric  acid  and,  after  a  half 
hour,  titrating  with  thiosulphate.  Following  these  directions  in 
assaying  a  spirit  that  gave  4-9  per  cent,  of  ethyl  nitrite  by  the  gaso- 
metric method,  the  results  ranged  from  2-6  to  3  2  per  cent.,  and 
when  the  solutions  were  left  undisturbed  for  a  few  moments  after 
titration  of  the  iodine,  iodine  was  liberated  at  the  surface,  showing 
it  to  be  effected  through  external  influence. 
With  the  use  of  acetic  instead  of  sulphuric  acid,  as  proposed  by 
Walker,  the  liberation  of  iodine  was  still  slower,  in  the  case  of  pro- 
tection from  the  influence  of  the  air  by  means  of  liquid  paraffin. 
Without  this  protection  it  was  considerably  faster,  but  due  nearly 
as  much  to  the  oxidizing  influence  of  the  air  as  to  reaction  within 
