Am.  Jour.  Pharm. 
July,  1884. 
Spirit  of  Nitrous  Ether. 
387 
clusively  than  another,  it  is,  that  water  encourages  the  decomposition 
of  the  ether.  "Whence  it  is  manifest  that  the  specific  gravity  ought 
to  be  kept  as  low  as  possible  consistent  with  the  clue  proportion  of 
ethyl  nitrite. 
Secondly,  "  it  effervesces  feebly  or  not  at  all  when  shaken  with  a 
little  bicarbonate  of  potash."  Not  much  can  be  said  against  this  test, 
though  it  is  perhaps  a  little  indefinite.  It  might  be  better  to  have  a 
limit  fixed  to  the  amount  of  free  acid,  the  same  to  be  determined  by 
standard  alkali — but  this  is  doubtful. 
Thirdly,  "  if  it  be  agitated  with  twice  its  volume  of  saturated  solu- 
tion of  chloride  of  calcium  in  a  closed  tube,  2  per  cent,  of  its  original 
volume  will  separate  in  the  form  of  nitrous  ether  and  rise  to  the  surface 
of  the  mixture."  This  test  has  given  rise  to  much  controversy.  It 
belongs  to  the  class  of  inaccurate  empirical  tests,  which  are  always  un- 
satisfactory, though  sometimes  tolerable  when  nothing  better  can  be 
obtained.  Chemists  have  all  recognized  that  the  "  ethereal  fluid," 
which  separates  under  the  above  circumstances,  is  not  ethyl  nitrite,  but 
a  solution  of  the  same,  of  variable  strength.  It  is  probably  just  as 
well  that  it  is  so,  especially  when  the  testing  is  performed  on  a  warm 
summer  day.  Judging  from  some  estimations  which  I  made  by  the 
method  subsequently  described,  this  etheric  fluid  would  seem  to  con- 
tain from  50  per  cent,  to  60  per  cent,  of  nitrous  ether.  Professor 
Attfield1  says  that  it  contains  less  than  half  its  bulk  of  ethyl  nitrite. 
Professor  Redwood2  is  responsible  for  the  generally  accepted  belief 
that  2  per  cent,  of  separation  indicates  10  per  cent,  of  ether.  If  made 
regarding  the  "  ethereal  fluid,"  which  actually  separates,  the  statement 
may  be  fairly  correct,  but  it  is  quite  untrue  if  applied  to  a  10  per  cent, 
solution  of  ethyl  nitrite  in  spirit.  Such  a  solution  will  separate  more 
than  half  its  contained  ether  when  agitated  with  solution  of  calcium 
chloride.  I  have  tried  many  experiments  with  this  test,  but  it  would 
be  superfluous  to  detail  them.  Suffice  it  to  say  that  there  are  three 
main  factors  which  determine  the  amount  separated  : — 
1st.  The  composition  of  the  spirit. 
2d.  The  temperature. 
3d.  The  dimensions  of  the  tube. 
Regarding  the  first  of  these  I  would  only  remark  that  if  the  spirit 
1  "  Pharm.  Journ.,"  [3],  viii.,  378. 
-  "  Pharm.  Journ.,"  [2],  viii,  508. 
