254  ON  THE  IGNITING  POINT  OF  VAPORS,  ETC. 
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Sherry  wine 
•993 
130 
Port  wine 
1-003 
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Refined  paraffin  oil 
•809 
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123 
Ditto 
•814 
138 
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Fusel  oil 
•850 
140 
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Resin  oil 
•987 
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212 
Heavy  pitch  oil 
•950 
212 
It  will  be  observed  that  the  specific  gravity  bears  no  relation  to 
the  temperature  required  to  expel  vapor  from  many  of  the  pro- 
ducts mentioned  in  the  table,  and  this,  in  some  instances,  arises 
from  the  fact  that  they  are  not  isolated  chemical  substances, 
but  consist  of  distinct  compound  bodies  mixed  together,  the 
lighter  of  which  usually,  but  not  always,  distils  off  first.  This 
is  very  well  shown  from  the  results  obtained  in  experimenting 
on  the  two  samples  of  crude  and  the  sample  of  burning  naphtha, 
the  benzole  having  been  separated  from  the  latter  by  fractional 
distillation.  In  the  crude  naphtha  there  always  exists  a  large 
proportion  of  tarry  matter  and  naphthaline,  and  with  a  gravity 
approaching  to  -890  as  compared  with  burning  naphtha,  which 
has  been  freed  from  all  tarry  matter,  and  has  a  gravity  not  ex- 
ceeding -860 ;  it  is  not  to  be  expected  that  the  crude  will  give 
off  vapor  as  readily  as  the  refined.  This  has  been  the  case, 
however,  as  is  indicated  by  the  table  of  results.  The  crude  gave 
off  vapor  at  a  much  lower  temperature  than  the  refined  burning 
naphtha  ;  and  the  same  remark  applies  to  the  results  obtained 
from  crude  and  refined  parafiin  oils  from  which  paraffin  spirit 
has  been  separated.  In  the  case  of  spirit  of  wine  and  different 
proportions  of  water,  and  also  of  liquids  that  will  mix  with  water, 
a  deduction  from  the  specific  gravity  might  be  made,  which 
would  at  once  indicate  the  igniting  point  of  the  vapor,  and  also 
