736 
Purified  Ether. 
/Am.  Jour.  Pharm. 
November,  1919. 
5  Cc.  of  10  per  cent,  alcohol,  which  was  separated.  Two  further 
washings  were  rejected,  but  the  fourth  reserved.  It  was  then 
further  washed  with  two  lots  of  5  Cc.  of  water,  the  second  lot  being 
reserved  for  the  test.  The  results  are  shown  in  the  table,  quantities 
being  Cc.  methyl  alcohol. 
Sample. 
10 
i  Alcoholic  Extract. 
Aqueous  Extract. 
I  St 
4th 
2d 
Rectified  
.001 
.0002  (say) 
nil 
.0015 
Very  faintly  blue  nil 
nil 
Meth.  (low  boiling  point)  
.0015 
.0006  (say) 
.002 
Meth.  (low  boiling  point)  
.0025 
.0004  (say) 
.001 
And  if  two  portions  of  the  same  sample  of  ether  be  extracted,  one 
with  10  per  cent,  alcohol  and  the  other  with  water  only,  and  the 
test  applied,  the  difference  between  the  two  results  varies  with  dif- 
ferent makes  of  ether — the  aqueous  extract  from  one  ether  may 
give  twice  as  strong  an  indication  as  the  alcoholic  extract,  while  with 
another  ether  it  may  be  six  or  even  more  times  as  great.  Of  course, 
the  effect  in  aqueous  solution  is  not  to  be  compared  with  that  in  the 
10  per  cent,  alcohol,  on  account  of  the  increased  oxidizing  power  of 
the  permanganate  where  the  alcohol  is  absent. 
But  the  experiment  shows  that  while  with  some  samples  there 
are  impurities  extractable  by  alcohol,  leaving  no  other  oxidizable 
bodies  behind,  yet  with  others  we  may  have  the  same  impurities  and 
further  traces  of  other  oxidizable  substances  as  well.  In  short,  the 
impurities  vary  with  different  ethers. 
Rather  than  attempting  any  method  of  overcoming  the  inherent 
"  ether  effect "  in  this  test,  and  bearing  in  mind  the  possibility  of 
variation  in  its  behavior  in  different  hands,  it  is  suggested  that  com- 
parison against  a  given  standard  is  much  better  than  demanding  a 
negative  reaction.  Such  a  procedure  not  only  has  the  obvious  ad- 
vantage of  being  definite,  but  also  ensures  the  proper  working  of 
the  test,  and  gives  evidence  at  once  if  the  reagents  are  insufficiently 
sensitive.  Probably  a  limit  of  an  apparent  0.05  per  cent,  of  methyl 
alcohol  would  be  quite  fair  for  a  modern  purified  ether  from  methy- 
lated spirit.  As  to  other  impurities,  since  they  are  not  specially 
guarded  against  in  the  Pharmacopoeia,  one  may  assume  that  such  as 
occur  in  the  usual  course  of  events  are  not  considered  objectionable 
from  the  medical  point  of  view.  But  the  finding  of  the  trace  of 
formaldehyde  in  a  sample  of  rectified  ether  which  had  been  in  stock 
