MANUFACTURE,  IMPURITIES  AND  TESTS  OF  CHLOROFORM.  435 
to  be  hurtful.  A  trace  of  acetic  ether  is  often  present  in  very 
good  chloroform,  even  to  an  extent  perceptible  in  the  odor,  but 
it  is  not  at  all  hurtful  in  such  proportion.  Chlorinated  lime 
containing  twenty-seven  per  cent,  of  chlorine  or  hypochlorite, 
■will  yield,  with  the  above  process  and  management,  seven  per 
cent,  of  its  weight  in  pure  chloroform.  And  the  alcohol  used 
will  yield  ninety-two  per  cent,  of  the  weight  of  the  absolute 
alcohol  it  may  contain  ;  or  alcohol  of  ninety-one  per  cent,  will 
yield  83.7  per  cent,  of  its  weight  of  finished  chloroform. 
The  writer  avoids  in  this  place,  as  foreign  to  the  intended 
practical  and  medical  character  of  this  paper,  all  discussion  of 
the  theory  and  reactions  of  tbe  process.  It  is  sufficient  to  say 
that  chloroform  is  generally  regarded  as  a  terchloride  of  formyle, 
and  has  the  ultimate  formula  C2,  H.  CL.  The  chemically  pure 
chloroform  as  represented  by  this  formula  should  practically  be 
associated  with  a  little  alcohol,  and  perhaps  water,  in  order  that 
it  may  keep  well  without  troublesome  precautions.  That  pro- 
duced by  the  above  process  contains  a  little  water,  but  is  almost 
chemically  free  from  alcohol,  and  as  produced  is  liable  to  slight 
decomposition  with  the  production  of  free  chlorine.  Hence  it  is 
useful  and  proper  to  add  a  small  proportion  of  ordinary  alcohol, 
so  that  the  s.  g.  may  be  reduced  from  1.498  to  the  officinal  stand- 
ard, namely,  1.49,  or  at  least  to  1.494. 
The  writer  is  convinced  by  observations  upon  chloroform 
made  by  himself,  that  a  tendency  to  decomposition  becomes 
very  strong  when  chloroform  has  a  purity  indicated  by  a  density 
above  1.497,  and  that  decomposition  will  be  almost  inevitable 
when  the  density  is  above  1.498,  and  he  believes  that  this  cir- 
cumstance explains  the  fact  that  chloroform  which  has  been 
purified  with  concentrated  sulphuric  acid  alone,  rarely  keeps 
well,  although  known  then  to  be  almost  chemically  pure.  The 
acid  abstracts  not  only  the  impurities  as  such,  but  also  the  last 
portions  of  water  and  alcohol.  Then  when  a  single  point  of 
decomposition  is  determined  by  light  or  other  incitant  to  chemi- 
cal reaction,  that  reaction  proceeds  as  in  a  process  of  fermen- 
tation until  the  whole  is  decomposed.  The  small  proportion  of 
alcohol  may  prevent  this  in  many  ways,  but  probably  by  closing 
the  circuit  of  the  composition  of  the  compound  as  the  circuit  of 
the  magnet  is  closed  by  its  keeper,  or  as  the  decomposing  forces 
