304 
ON  CHLOROFORM. 
will  soon  rise  to  the  surface,  and  may  now  be  removed  without 
trouble  by  means  of  a  separatory  funnel.  This  is  by  far  the 
easiest  method  for  reducing  chloroform  to  any  given  specific 
gravity.  Even  if  the  pharmacopoeia  in  a  future  revision  should 
adhere  to  the  purification  of  chloroform  by  means  of  concentrated 
sulphuric  acid,  it  will  be  advisable  to  rectify  this  chloroform  per 
se  after  the  adhering  acid  has  been  removed  by  an  alkali,  and 
subsequently  dilute  it  with  alcohol,  separating  the  water  after  it 
has  collected  on  the  surface. 
I  have  never  experienced  any  difficulty  in  regenerating  chloro- 
form which  had  acquired  an  acid  reaction.  Such  chloroform  was 
always  made  from  ordinary  alcohol,  and  had  previously  been 
rectified.  If  such  an  acidified  chloroform  was,  agitated  with  a 
solution  of  carbonate  of  soda,  and  subsequently  distilled  over  a 
little  unslaked  lime,  it  was  always  obtained  of  an  unexceptionable 
reaction.  The  same  result  was  arrived  at  by  diluting  the  chloro- 
form with  some  alcohol,  agitating  them  well  together,  and  filter- 
ing the  turbid  mixture  at  once  through  a  plain  filter,  covered  with 
a  quantity  of  dry  carbonate  of  potassa.  Chloroform  regenerated 
in  this  way,  and  diluted  to  the  specific  gravity  of  1*475,  has  kept 
in  the  diffused  daylight,  and  even  exposed  to  sunlight,  without 
any  perceptible  change.  If  chloroform  is  prepared  from  other 
material  than  alcohol,  the  regeneration  may  probably  be  more 
difficult. 
A  slight  acid  reaction  in  chloroform  is  not  readily  ascertained 
by  holding  a  piece  of  litmus  paper  in  it,  since  the  coloring  matter 
of  litmus  is  utterly  insoluble  in  this  liquid.  The  most  minute 
acid  reaction  is  best  observed  by  evaporating  spontaneously  a 
few  drops  of  chloroform  with  a  drop  of  an  aqueous  solution  of 
litmus,  properly  neutralized.  A  minute  trace  of  acid  will  then 
change  this  color  to  a  reddish  tint,  and  no  acid  will  be  lost  by 
and  with  the  evaporation  of  the  chloroform,  since  the  aqueous 
litmus  floats  on  the  surface,  just  in  the  place  where  it  is  best 
calculated  to  absorb  any  acid  which  may  be  present. 
Chloroform,  I  believe,  is  best  kept  in  cork-stoppered  bottles ; 
it  has  no  influence  upon  the  cork,  but,  if  it  should  acquire  free 
acid,  this  would  soon  show  itself  by  imparting  to  the  lower  end 
of  the  cork  a  yellow  color,  and  softening  its  texture  so  that  it 
readily  crumbles  to  pieces  when  rubbed  between  the  fingers. 
