Am.  Jour.  Pharm. 
July,  1884. 
Spirit  of  Nitrous  Ether. 
389 
results.  This  is  not  surprising  considering  the  facility  with  which 
potassic  permanganate  is  reduced,  and  the  certainty  that  there  are 
organic  compounds  present  after  evaporation  even  to  dryness.  Oxida- 
tion of  ferrous  sulphate  was  next  tried,  but  from  the  difficulty  of 
estimating  the  excess  of  ferrous  salt  in  the  presence  of  alcohol,  and 
from  other  causes,  the  process  proved  abortive.  Volumetric  solution 
of  urea  was  then  employed,  iodized  starch  solution  being  used 
to  indicate  the  end  of  the  reaction,  but  this  plan  proved  entirely  un- 
successful, chiefly  on  account  of  the  impossibility  of  observing  a  definite 
end-point.  Possibly,  however,  the  urea  method  might  be  made  availa- 
ble by  measuring  the  N,  or  weighing  the  C02  evolved  ;  that  is  to  say 
if  the  reaction  goes  as  it  ought.  CON2H4-[-2HN02=C02+N4-|-3H26. 
The  nitrous  ether  might  possibly  be  estimated  by  reducing  with 
hydric  sulphide,  but  I  have  not  had  time  to  thoroughly  examine  this 
reaction.  The  few  experiments  I  have  been  able  to  perforin  with  it 
did  not  yield  promising  results. 
After  innumerable  experiments  I  have  been  compelled  to  return  to 
the  method  which  suggested  itself  to  me  first  of  all,  viz.,  the  libera- 
tion of  iodine  from  potassic  iodide,  and  titration  of  the  iodine  with 
sodium  thiosulphate  The  only  mention  I  have  seen  of  the  use  of 
potassium  iodide  as  a  means  of  estimating  spiritus  setheris  nitrosi,  is 
reported  in  the  "  Pharmaceutical  Journal."1  In  the  discussion  after  the 
reading  of  Dr.  Dupre's  paper,  Mr.  Hehner  suggested  the  use  of  iodide 
of  potassium  added  directly,  with  addition  of  acetic  acid,  which  was 
thought  a  good  idea.  The  process  is  so  obvious,  that  it  has  probably 
often  been  tried  and  abandoned,  which  would  not  be  surprising,  as 
without  particular  precautions  it  yields  results  which  have  no  resem- 
blance to  the  truth.  In  endeavoring  to  put  this  test  into  practical 
form,  I  very  soon  found  that  the  only  way  of  arriving  at  right  results 
was  to  work  with  a  solution  of  ethyl  nitrite  of  known  strength ;  at 
least  in  the  first  place.  We  therefore  purified  some  of  the  nitrite  by  a 
method  similar  to  that  described  by  Mr.  Williams.2  At  60°F.  it  had 
a  specific  gravity  of  '901  (or  thereby).  Mr.  Williams  gives  the  gravity 
as  '937,  but  states  no  temperature.  At  all  events,  though  it  was  not 
analysed,  I  am  confident  that  it  must  have  been  very  nearly  pure. 
Ten  cc.  were  diluted  to  100  cc.  with  "  absolute "  alcohol,  and  this 
solution  was  used  in  the  experiments. 
1  [3],  x.,  93. 
2  "Pharm.  Journ.,"  [3],  viii.,  442. 
