Am.  Jour.  Pharm. 
June,  1897. 
Spirit  of  Nitrons  Ether. 
309 
ning  of  this  article,  my  attention  was  attracted  by  the  controversy 
referred  to,  and  I  undertook  some  experiments  with  the  titration 
method  as  proposed  by  Professor  Walker,  in  order  to  ascertain  if  it 
could  be  placed  in  the  hands  of  pharmacists  as  a  practical  method. 
In  the  first  set  of  titrations,  sufficient  decinormal  sodium  thio- 
sulphate  volumetric  solution  was  added  to  discharge  the  bluish- 
green  color,  so  that  it  did  not  return  in  thirty  seconds.  The  reason 
for  adopting  this  plan  was  to  afford  the  operator  proof  that  decolor- 
ation had  been  effected.  The  color  quickly  reappeared  after  decolor- 
ation on  account  of  the  liberation  of  iodine  by  the  nitrogen  tetroxide, 
as  pointed  out  by  Mr.  MacEwan.  This  reaction  is  also,  of  course, 
going  on  from  the  time  the  materials  are  mixed,  and  even  during 
titration,  so  that  iodine  is  being  alternately  liberated  and  titrated. 
The  tendency  of  the  method  must,  therefore,  be  toward  high  results, 
for  the  same  iodine  is  repeatedly  taken  into  account.  The  rapidity 
with  which  the  volumetric  solution  of  sodium  thiosulphate  is  added, 
as  also  the  quantity  added  at  a  time,  influences  the  amount  required 
for  decoloration.  The  more  rapid  the  addition  of  sodium  thiosul- 
phate and  the  larger  the  portion  added,  the  less  the  total  quantity 
required  for  the  first  decoloration. 
The  following  figures  show  the  amounts  of  decinormal  sodium 
thiosulphate  volumetric  solution  required  for  the  titration  of  the 
iodine  liberated  by  portions  of  5  c.c.  of  a  few  of  the  samples  of  spirit 
of  nitrous  ether  examined  : 
Sample 
Minutes 
No 
Macerated. 
.  C.C.  of  V.  S.  Required. 
15 
247,  23-1,  14-4,  14-0 
15 
14*2,  l6'I,  ICT2,  IO7 
3 
15 
20'5,  20'2,  l8'9,  19*4 
15 
28*2,  28-3,  32*2 
5 
15 
f  30*4,  30-8,  33-6,  34-5 
^35'3>  37*3,  37'3,  32*o 
5 
IO 
25-2,  27-3 
5 
5  . 
24-6,  20*6 
The  titrations  were  conducted  as  nearly  alike  as  possible.  The 
figures  for  sample  5  also  show  the  effects  of  the  time  of  maceration. 
After  concluding  that  the  titration  method  was  not  trustworthy, 
even  when  conducted  under  the  conditions  and  restrictions  proposed, 
I  made  a  series  of  tests  with  the  nitrometer  according  to  the  United 
States  Pharmacopoeia  process  of  assay.     Two  difficulties  were 
