3.  Compounds  derived  from  Alcohol,  but  of  uncertain  constitution.
Olefiant  Gas.  SYN.  Hyduret  of  Acetyle.  Ethylene.
C*  H3  ,  H  =  Ac  H.  This  well-known  compound  is  generally
present  in  coal  gas,  oil  gas,  and,  in  general,  in  all  gaseous
mixtures  produced  by  the  action  of  heat  on  organic  substances.
It  is  best  obtained  pure  by  heating  1  part  of  alcohol  with  6  or  7
of  oil  of  vitriol,  adding  as  much  sand  as  will  convert  the  whole
into  a  paste,  which  prevents  the  frothing  that  would  otherwise
occur.  There  is  produced  some  ether,  then  sweet  oil  of  wine,
and  lastly,  a  mixture  of  sulphurous  acid  and  olefiant  gases.
By  passing  the  gas  through  milk  of  lime,  the  sulphurous
acid  is  removed,  and  by  then  passing  it  through  oil  of  vitriol,
the  ether,  alcohol,  and  water  which  may  be  present,  are  likewise
separated.  Pure  olefiant  gas  has  been  already  described  (see
Part  I.)  :  here  we  shall  attend  to  its  combinations,  premising
that  it  is  the  second  in  a  homologous  series  of  carbohydrogens,
of  which  methylene,  or  hyduret  of  formyle,  Ca  Ha  =  Ca  H,  H,  is
the  first.  It  is  absorbed  by  anhydrous  sulphuric  acid,  forming
the  crystalline  compound  formerly  mentioned,  2  S  Os  +0*114,
which,  in  contact  with  water,  produces  ethionic  acid.  When
mixed  with  its  own  volume  of  chlorine,  both  gases  are  condensed
into  a  liquid,  the  composition  of  which  is  C*  H*  Cls  .  This  is
the  oily  compound,  from  which  the  gas  was  called  olefiant  gas  :
the  oil  is  often  called  the  oil  of  the  Dutch  chemists,  having  been
discovered  by  an  association  of  chemists  in  Holland.
