THE  AMERICAN 
JOURNAL  OF  PHARMACY 
MARCH,  igo8 
ESTIMATION  OF  ALCOHOL  IN  CONCENTRATED 
NITROUS  ETHER. 
By  W.  A.  Pearson. 
In  searching  for  an  accurate  method  for  determining  alcohol  in 
concentrated  nitrous  ether,  I  tried  the  method  described  by  Dupre 
(Allen,  Vol.  I,  page  102  and  J.A.C.S.,  Vol.  XX,  page  495)  and  found 
it  to  be  very  accurate  for  dilute  alcoholic  solutions  containing  from 
O'l  gramme  to  0-3  gramme  in  20  c.c.  The  accuracy  was  tried  on 
dilute  solutions  of  alcohol  of  known  strength,  the  results  of  analyses 
differing  from  the  actual  amount  of  alcohol  present  by  only  one  or 
two  units  in  the  second  decimal  place,  if  proper  conditions  are 
observed. 
The  next  step  was  to  separate  the  alcohol  from  the  nitrous  ether. 
Various  methods  were  tried,  with  varying  success,  but  the  evapora- 
tion of  the  concentrated  nitrous  ether  in  a  flask  containing  water, 
and  passing  the  vapor  through  water  seemed  advantageous.  At 
first  a  small  Erlenmeyer  flask  about  one-fourth  full  of  ice-water  was 
weighed  accurately,  20  to  35  grammes  of  concentrated  nitrous 
ether  poured  in,  and  again  accurately  weighed.  Anticipating  your 
objections  to  direct  weighing  of  so  volatile  a  liquid  under  these 
conditions,  will  say  that  only  a  very  slight  error  will  be  made  if 
flask  and  concentrated  nitrous  ether  are  very  cold  and  having  the 
subsequent  apparatus  near  the  scales,  ready  to  be  connected  with 
the  flask.  The  proper  weights  are  placed  on  the  scales  slightly 
below  the  correct  weight  of  flask,  ice-water  and  concentrated  nitrous 
ether,  and  as  the  weight  changes,  at  the  proper  moment  remove  the 
flask  from  scales  and  connect  at  once  with  the  apparatus. 
If  this  method  be  carefully  followed  not  more  than  1  milligramme 
(KM) 
