AmAu,r'^7arm*}  SPirit  of  Nitrous  Ether.  365 
431*518  grains  (water  weighing  455*669  grains),  and  1928*5  grains  of 
nitrous  ether  will,  therefore,  measure  4*469  fluidounces,  which,  being 
contained  in  107  flouidounces  of  finished  spirit  of  nitrous  ether,  gives 
a  possible  quantity  of  absolute  nitrous  ether  in  the  spirit  of  the  U.  S.  P. 
of  4*1766  per  cent. 
I  am  not  disposed  to  quarrel  with  the  revisors  of  the  "  Pharmaco- 
poeia," but  cannot  help  thinking  that  a  more  careful  perusal  of  the 
original  paper  of  Prof.  Redwood  would  have  prevented  this  error. 
Speaking  of  the  15  fluidounces  of  distillate  obtained  by  the  process, 
Prof.  Redwood  says1:  "  This  product  consists  of  a  strong  spirituous 
solution  of  nitrous  ether  containing  thirtyflve  per  cent,  of  crude  ether 
and  further  on,  when  speaking  of  the  finished  product  :  "  If  it  be 
mixed  with  twice  its  volume  of  a  concentrated  solution  of  chloride  of 
calcium,  from  two  to  three  per  cent,  of  nitrous  ether  will  separate  and 
rise  to  the  surface  of  the  liquid.  This  indicates  the  presence  of  ten 
per  cent,  of  ether,  as  eight  per  cent,  remains  unseparated.*'  In  no 
portion  of  his  paper  does  Prof.  Redwood  claim  that  he  has  operated 
with,  or  obtained,  absolute  nitrous  ether  ;  but,  speaking  of  crude  ether 
in  connection  with  the  percentage  in  the  distillate,  it  is  fair  to  assume 
that  crude  ether  is  also  meant  when  speaking  of  the  percentage  sepa- 
rated from,  and  contained  in  the  finished  spirit.  Indeed,  if  the  15 
fluidounces  of  distillate  contain  35  per  cent,  of  crude  ether,  the  finished 
spirit  made  from  it — 55  fluidounces — can  not  contain  quite  10  per 
cent,  of  crude  ether,  as  is  shown  by  the  following  calculation  : 
15  fluidounces  of  distillate  contain  35  per  cent.,  or  5*25  fluidounces 
of  crude  ether  ;  consequently  this  quantity  is  contained  in  55  fluid- 
onnces  of  the  finished  spirit.  Then 
55  :  5"25  =:  100  :  9-945, 
proving  that  according  to  Prof.  Redwood's  own  showing  the  finished 
spirit  can  only  contain  9*945  per  cent,  of  crude  ether. 
I  do  not  intend  in.  the  present  paper  to  inquire  into  the  composition 
of  u  crude  nitrous  ether,"  within  the  meaning  of  Prof.  Redwood,  such 
an  inquiry  requiring  an  amount  of  research  for  which  I  have  no 
leisure.  It  is  an  established  fact,  that  by  any  and  all  methods  that 
have  hitherto  been  proposed,  it  is  extremely  difficult  to  obtain  pure 
and  absolute  nitrous  ether,  and  it  is  hardlv  probable  that  Prof.  Red- 
1  "Am  Jour.  Phar.,"  July,  1867,  p.  331. 
