388 
Spirit  of  Nitrous  Ether. 
(Am.  Jour.  Pharm. 
1       July,  1884. 
is  watery  it  will  give  a  better  result,  cceteris  paribus,  than  one  contain- 
ing less  water.  It  will  readily  be  understood  that  with  a  compound 
having  so  low  a  boiling  point,  and  so  high  a  vapor  pressure  at  ordinary 
temperatures  as  nitrous  ether,  the  proportion  separated  by  chloride  of 
calcium  solution  must  be  much  affected  by  the  second  and  third  of 
these  causes;  e.g.,  15  cc.  of  spiritus  setheris  nitrosi  at  48 °F.,  shaken 
up  with  two  vols,  solution  of  calcic  chloride  at  same  temp.,  gave  a 
separation  of  0*4  c  c.  When  the  experiment  was  repeated  with  the 
spiritus  and  chloride  solution  at  the  temp,  of  68 °F.,  separation  of 
only  02  cc.  was  obtained.  By  using  a  capacious  tube  in  one  case, 
and  in  another  a  Email  tube  which  the  mixture  nearly  filled,  results 
almost  as  variable  were  observed.  It  may  here  be  noted  that  the 
"  ethereal  fluid  "  takes  some  time  to  separate,  the  process  being  seldom 
complete  in  less  than  half  an  hour.  The  greatest  objection  to  this  test 
is,  however,  the  well-known  fact  that  a  genuine  preparation  will  after 
a  certain  time,  and  while  still  retaining  its  medicinal  virtues,  fail  to 
give  any  separated  "  ether  "  when  agitated  with  solution  of  chloride  of 
calcium.  Taking  all  the  facts  into  consideration,  I  am  clearly  of 
opinion  that  this  separation  test  ought  to  be  abolished. 
What  we  require  is  a  test  which  shall  sIioav  at  least  approximately 
the  value  of  the  preparation,  by  means  of  reagents  and  apparatus  at 
the  disposal  of  every  pharmacist.  This  must  be  done  by  estimating 
the  nitrous  acid,  whether  it  exists  as  such  or  potentially.  There  does 
not  appear  to  be  any  reason  for  making  a  separate  determination  of  the 
percentage  of  uncombined  nitrous  acid,  which  no  doubt  contributes  its 
share  to  the  physiological  action  of  the  substance.  Of  the  many 
methods  which  have  been  proposed  for  the  purpose  of  this  estimation, 
probably  the  best  is  <that  devised  by  Professor  Eykman,  of  Tokio. 
Not  that  I  regard  his  process  as  perfect,  because  I  believe  it  gives  re- 
sults distinctly  under  the  truth,  and  of  course  it  includes  the  nitric 
acid  should  any  be  present.  The  fatal  objection  to  Eykman's  process 
as  a  pharmacopoeial  test  is  the  elaborate  apparatus  and  nicety  of  mani- 
pulation required.  It  is,  in  short,  better  adapted  for  the  laboratory  of 
the  analyst  than  for  the  pharmacy ;  and  as  ail  the  official  tests  ought 
to  be  as  simple  as  possible,  we  must  endeavor  to  find  an  easier  method. 
I  have  tried  a  great  number  of  experiments  with  this  object,  and  have 
to  confess  that  the  result  after  all  is  not  a  complete  success.  The  old 
method  of  saponifying  with  caustic  soda,  and  after  evaporation  of  the 
alcohol,  titrating  with  permanganate,  was  found  to  yield  very  variable 
