AmjlZr;imarm-}     Amy  I  Nitrite  and  Nitrous  Ether.  281 
was  the  result  given  by  the  nitrite  alone,  indicating  that  the  impuri- 
ties usually  contained  in  ethyl  nitrite  do  not  raise,  but  rather  tend  to 
lower  the  results  of  the  method.  All  evidence  so  far  adduced,  then, 
tends  toward  the  same  direction,  i.  e.,  that  the  method  is  not  liable 
either  to  give  too  high  or  too  low  results  under  ordinary  conditions, 
and  that  under  abnormal  conditions  the  tendency  is  toward  low 
rather  than  high  results.  The  natural  inference,  therefore,  is  that 
the  results  of  Allen's  gasometric  method  are  always  too  low  in  the 
estimation  of  ethereal  nitrites. 
The  following  details  have  been  adopted  as  being  considered  the 
most  practical : 
Valuation  of  Spirit  of  Nitrous  Ether. — Into  a  100  c.c.  flask  or 
bottle  of  white  glass,  provided  with  a  loosely-fitting  stopper  of  glass, 
rubber  or  cork,  place  successively  10  c.c.  of  distilled  water,  5  c.c.  of 
a  cold,  aqueous,  saturated  solution  of  potassium  chlorate,  5  c.c.  of 
the  spirit  to  be  tested,  and  5  c.c.  of  10  percent,  nitric  acid.  Quickly 
insert  the  stopper  and  shake  frequently  during  thirty  minutes.  Then 
N 
add  10  c.c.  of  —  silver  nitrate,  shake  briskly  for  a  moment,  add  10 
10 
drops  of  ferric   ammonium  sulphate  solution,   and   titrate  the 
N 
excess  of  silver  with  —  potassium  sulphocyanate.  (The  titra- 
tion should  be  performed  without  delay,  to  avoid  darkening  of  the 
precipitated  silver  chloride  by  the  influence  of  light,  which  inter- 
feres with  the  end-reaction.)  The  end-point  is  reached  when,  after 
momentary  shaking,  upon  addition  of  the  last  drop  of  solution,  the 
appearing  red  color  is  not  entirely  dispersed,  but  leaves  the  liquid 
faintly  reddish  throughout.  The  color  will  frequently  disappear 
after  persistent  shaking  or  after  standing  a  while,  but  no  attention 
need  be  paid  to  this.  Assuming  the  spirit  to  contain  4  per  cent,  by 
weight  of  ethyl  nitrite,  and  to  have  a  specific  gravity  of  0-84,  it 
would  require  2-55  c.c.  _5L  potassium  sulphocyanate  to  precipitate 
N 
the  excess  of  silver  in  solution.    As  each  cubic  centimeter  of  — - 
10 
silver  nitrate  consumed  in  precipitating  the  chloride  formed  corre- 
sponds to  0  022 5  gramme  of  ethyl  nitrite,  the  calculation  is  as  follows: 
(10  —  2-z,K)  X  00221;  x  100 
v  DDJ  D    =  4-0  per  cent. 
5  X  0-84 
