CHLOROFORM  AND  THE  TESTS  FOR  ITS  PURITY  IN  P.  B.  291 
dirty  tube ;  one  cleaned  with  a  woolly  cloth,  off  which  some 
fibres  are  left  behind ;  the  contact  of  the  finger  if  employed  to 
close  the  tube  while  agitating  the  fluids ;  or  some  organic  sub- 
stance accidentally  present, — will  all  give  more  or  less  color  to 
the  acid.  With  the  precautions  mentioned,  the  S  03  test  is  a 
perfectly  fair  and  most  useful  one.  One  other  caution  may  be 
proper  here,  and  that  is,  do  not  return  the  sample  tested  with 
S  03  to  the  stock ;  Chloroform  twice  treated  with  S  03,  Chris- 
tison  states,  is  likely  to  decompose. 
The  third,  that  it  "  leaves  after  evaporation  no  residue,  and 
no  unpleasant  odor,"  is,  for  the  Pharmaceutical  Chemist  and  the 
physician,  the  most  important  of  them  all;  but  it  needs  a  few 
words  regarding  the  olfactory  part  of  it  It  is  only  a  very  im- 
pure chloroform  that  will  leave,  in  the  ordinary  sense  of  the 
word,  any  unpleasant  odor  after  its  evaporation;  and  sometimes 
it  happens  that  what  is  left,  is  of  a  rather  pleasant  flavor.  And 
again,  when  chloroform,  containing  only  a  minute  quantity  of 
those  deleterious  oils  formed  with  itself  in  the  process  of  its 
preparation,  is  left  to  evaporate  from  a  clean  cloth  or  vessel,  it 
is  only  at  the  last  moment  their  offensive  smell  is  felt  ;  and  if 
the  sense  of  smell  is  not  delicate  and  on  the  closest  watch,  it 
will  not  discover  the  taint,  for  it  passes  off  instantly. 
We  come  now  to  the  fourth  test  given ;  it  "evolves  no  gas 
when  potassium  is  dropped  into  it." 
About  three  weeks  ago  we  got  notice,  from  one  of  the  most 
respectable  houses  in  London,  that  the  chloroform  we  had  sent 
them  did  not  stand  the  potassium  test  of  the  British  Pharmaco- 
poeia. From  the  first  we  held  the  test  to  be  inapplicable,  and 
such  as,  with  the  specific  gravity  given  in  the  British  Pharma- 
copoeia, ought  not  to  be  applied  to  it.  We  have  the  authority 
of  Gregory  and  others  that  the  specific  gravity  of  pure  chloro- 
form is  1*500,  and  our  own  experiments  assert  the  same  thing. 
A  specific  gravity  of  1-496,  then, -could  only  be  the  truth  when 
the  chloroform  contained  alcohol  or  water,  or  both ;  and  to  ad- 
mit into  the  Pharmacopoeia  a  chloroform  containing  those  fluids, 
and  then  to  apply  a  test  for  them,  and  reject  the  chloroform  be- 
cause they  were  present,  seemed  to  us  contradictory,  and  what 
could  not  have  been  the  intention  of  the  editors.  We  accord- 
ingly wrote  our  friends  to  the  above  purpose,  and  telling  them 
