298 
ON  CHLOROFORM. 
by  rectifying  it  in  contact  with  a  sufficient  amount  of  perman- 
ganate of  potassa,  or  sometimes  bichromate  of  potassa  and  some 
sulphuric  acid.  Those  powerful  oxidizers,  permanganic  and 
chromic  acid,  destroy  many  odorous  principles  of  vegetables 
before  they  oxidize  the  alcohol ;  exceptions  are  certain  volatile 
oils,  particularly  the  carbohydrogens  and  those-  containing  little 
oxygen.  But  alcohol  obtained  from  colchicum,  gentian,  aconite, 
belladonna  leaves,  &c,  was  by  this  process  completely  restored 
and  rendered  fit  for  use,  to  be  sure  with  the  loss  of  a  little  alco- 
hol, which  is  destroyed  by  the  excess  of  the  oxidizing  agents 
employed.  Chlorine  acts  in  a  similar  way,  and  if  it  should  pro- 
duce any  liquid  chlorinated  compounds  by  reacting  with  these 
odorous  principles,  they  are  most  assuredly  removed  by  the  sub- 
sequent treatment  with  oil  of  vitriol  and  the  following  rectifica- 
tion. It  is  more  than  probable  that  even  the  presence  of  con- 
siderable amounts  of  volatile  oils  in  the  alcohol  would  merely 
occasion  a  loss  of  chlorine,  but  be  without  effect  on  the  purity  of 
the  chloroform,  because  all  the  chlorinated  products  of  the  vola- 
tile oils  boil  at  a  much  higher  temperature. 
The  effect  of  sulphuric  acid  upon  chloroform  has  been  fre- 
quently the  subject  of  investigation.  It  is  true,  as  stated  by 
Dumas,*  that  chloroform,  kept  over  sulphuric  acid,  will  evolve 
hydrochloric  acid,  but  this  decomposition  takes  place  only  in  the 
light,  while,  if  the  mixture  is  kept  in  blackened  bottles,  it  will 
keep  perfectly  well.  Nor  does  the  purification  with  sulphuric 
acid  render  chloroform  prone  to  subsequent  decomposition,  as  is 
proven  by  the  statement  of  Wiggers,  cited  above,  which  accords 
with  my  own  experience.  It  is  most  undoubtedly  the  case,  as 
was  first  stated  by  Gregory  and  afterwards  by  Dr.  Squibb,  that 
the  sole  cause  of  the  decomposition  of  chloroform  upon  the 
shelves  of  our  stores,  is  due  to  its  concentration,  to  its  freedom 
from  alcohol. 
The  specific  gravity  of  absolute  chloroform  is  about  1*50,  of 
which  density  I  have  repeatedly  obtained  it,  and  in  this  respect 
I  can  only  reiterate  the  statements  of  Hirsch  and  others.  The 
true  specific  gravity  of  absolute  chloroform  has  probably  not  been 
Ann.  de  Chim.  et  de  Phys.  lvi,  115. 
