66 
PREPARATION  OF  ALCOHOL  IN  WINES. 
to  cool.  By  this  operation  you  will  have  expelled  not  only  all 
the  spirit,  but  a  good  portion  of  water  with  it. 
Next  make  this  residuary  liquor  containing  the  sugar  and 
other  extractive  matter  of  the  wine,  minus  its  alcohol,  up  to  the 
original  bulk  with  distilled  water,  and  take  its  specific  gravity, 
which  in  this  case  will  be  1-020.  If  this  excess  of  20  over  the 
weight  of  the  standard  of  distilled  water  be  deducted  from  the 
specific  gravity  of  the  wine  thus,- — 
•997  including  its  spirit,  water,  and  other  extractive  matter  of 
the  grape ; 
20  amount  of  extractive  matter  in  the  water  only ; 
•977  will  be  the  true  specific  gravity  of  the  spirit  and  water 
contained  in  the  wine,  minus  the  extractive  matter,  which 
equal  to  17  per  cent,  of  alcohol,  according  to  the  published  tables 
of  alcoholic  strengths  at  different  densities  and  temperatures. 
Or,  which  is  nearly  the  same  thing,  we  may  proceed  by  sub- 
tracting the  specific  gravity  of  the  wine,  -997,  from  the  residu- 
ary liquor,  thus  1-020 
997 
leaving  -23,  which,  deducted  from  the  standard  of 
distilled    water  1000 
23 
leaves  -977  as  the  true  specific  gravity  of  the  spirit 
and  water  in  the  wine. 
These  examples  may  be  further  verified  by  a  distillatory  ex- 
periment thus  : — Take  5  ounces  of  the  wine  ;  distil  off  exactly 
half  by  a  gentle  heat  from  a  graduated  retort  to  which  a  receiver 
is  connected  till  oiliness  ceases  to  form  in  the  tube  end  of  the 
retort,  indicating  that  all  the  alcohol  has  passed  over.  The 
specific  gravity  of  this  distillate  (consisting  of  spirit  and  water) 
will  be  -955,  equal  to  34  per  cent.,  which,  divided  by  2, — as 
only  half  the  bulk  has  been  drawn  over — gives  17  per  cent.  Or 
the  distillate  may  be  diluted  with  its  own  bulk  of  distilled  water 
up  to  the  original  5  ounces,  when  its  specific  gravity  will  be  -9773 
equal  to  17  per  cent,  of  alcohol. 
