Am.  Jour.  Pharm. 
May,  1892. 
Imparity  in  Chloroform, 
239 
produced  with  it,  such  statements  can  only  be  based  on  theory.  It 
cannot,  however,  be  denied  that  all  chloroform  is  not  so  free  from 
impurity  as  it  should  be,  and  a  recent  examination  of  commer- 
cial samples  shows  that  in  some  cases  there  is  great  room  for  improve- 
ment. 
The  purity  of  chloroform  cannot  be  determined  by  any  one  test; 
those  of  the  Pharmacopoeia  enable  us  to  ascertain  its  purity  up  to 
a  certain  point,  but  beyond  that  there  has  been  no  attempt  made  to 
insist  on  a  purer  preparation,  or  to  provide  means  by  which  smaller 
quantities  of  impurity  not  recognized  by  the  P.  B.  tests  may  be 
detected  and  separated. 
Before  giving  a  process  for  recognizing  and  separating  impurities 
passed  over  by  the  P.  B.  tests,  I  would  like  to  point  out  that 
these  impurities  have  boiling  points  both  above  and  below  that  of 
pure  chloroform,  that  as  a  rule  they  possess  very  strong  character- 
istic odors  which  even  in  a  very  dilute  form  can  be  more  readily 
detected  by  the  nose  than  by  any  known  chemical  reagent,  and  fur- 
ther that  if  the  impurities  found  in  chloroform  are  dangerous  to  life, 
there  is  a  greater  likelihood  of  the  more  volatile  ones  doing  mis- 
chief than  the  less  volatile,  seeing  that  the  former  will  evaporate 
and  be  inhaled  with  the  chloroform,  while  the  latter  are  to  a  very 
large  extent  left  behind  when  the  chloroform  has  evaporated. 
At  present  no  process  is  known  by  which  the  total  impurity  in 
chloroform  can  be  determined.  By  careful  fractional  distillation, 
however,  and  dividing  the  sample  under  examination  into  two  frac- 
tions, one  of  10  per  cent.,  the  other  of  75  per  cent.,  and  a  residue 
of  15  per  cent.,  we  obtain  both  the  more  and  less  volatile  impurities 
in  a  concentrated  form.  Unfortunately  we  can  only  say  of  the  10 
per  cent,  fraction  that  it  does  not  in  a  greater  or  less  degree  possess 
the  smell  peculiar  to  impurity;  we  can  also  say  of  the  15  per  cent 
residue,  and  in  addition  collect  and  weigh  tjie  bulk  of  the  non-vola- 
tile impurity  by  slowly  evaporating,  with  precautions  to  exclude 
dust,  at  a  temperature  of  from  8o°  to  900  F. 
I  do  not  claim  that  the  result  obtained  by  this  process  give  the 
total  quantity  of  impurity  present  in  the  sample,  but  I  think  they 
are  of  considerable  comparative  value,  and  enable  us  to  reject 
inferior  chloroform,  which  at  present  passes  the  Pharmacopoeia 
standard. 
Seven  samples  of  commercial  chloroform,  which  were  found  to 
