Am.  Jour.  Pharm. ) 
Sept.,  1882  j 
Analysis  of  Wine. 
447 
-exti'act  in  a  wine  can  be  ascertained  from  the  specific  gravity  of  the 
liquid  after  being  deprived  of  alcohol.  In  almost  all  the  completely 
normal  wines  the  quantity  of  extract  found  by  the  above  method  cor- 
responded within  two  to  three  hundredths  per  cent,  to  that  indicated 
by  Hager's  table.  If  the  wine  contains  sugar  still  unfermented,  or 
unfermentable  constituents  of  potato  sugar^  then  usually  the  extract 
•calculated  is  somewhat  higher  than  what  is  found  ;  but  if,  on  the  con- 
trary, it  contains  an  abnormal  quantity  of  glycerin  the  extract  calcu- 
lated is  considerably  less  than  what  is  actually  found.  Therefore,  it 
is  always  advantageous  to  compare  the  amount  of  extract  calculated 
according  to  Hager's  tables  with  that  found  by  the  method  described. 
This  method  does  not  do  away  with  the  necessity  for  an  estimation  of 
the  glycerin  itself  in  such  wines  as  may  be  suspected  to  have  received 
an  addition  of  glycerin. 
Tlie  authors  have  applied  this  method  in  the  estimation  of  the  extract 
■of  several  hundred  kinds  of  undoubtedl}'  genuine  wines  of  different 
years  and  from  widely  separated  districts.  The  results  of  these  deter- 
minations are  set  out  in  a  tabular  form  in  a  separate  communication.^ 
It  was  found  that  the  absolute  quantity  of  extract  in  pure  natural 
wines  may  vary  within  very  wide  limits.  Among  other  conditions 
exercising  an  essential  influence  upon  it  are  the  nature  of  tlie  soil  of  the 
district  in  which  the  wine  is  grown,  the  situation  of  the  particnlar  vine- 
yard, the  weather,  degree  of  ripeness  of  the  grapes,  the  course  of  the 
fermentation,  and  unskillful  treatment  of  the  wine,  whicli  may  induce 
a  considerable  alteration  in  the  composition  of  tlie  extract  ithout  anv 
foreign  addition  being  made. 
The  amount  of  extract  present  in  pure,  completely  fermented  \vine 
stands  in  definite  relation  to  the  acid  ])resent.  It  amounted  in  none  of 
the  genuine  wines  examined  by  the  authors,  after  the  deduction  of  the 
free  acid  of  the  wine,  to  less  than  1  per  cent.  It  may  happe])  that  a 
genuine  wine  may  contain  less  than  1  per  cent,  of  extract  free  from 
acid;  but  in  such  cases  the  ^lon-tJo/c/ii/e  acid  is  determined,  Mud  after 
deducting  this  fixed  acid  from  the  total  extract  there  is  always  a  residue, 
amounting  to  at  least  1*1  per  cent.  The  estimation  of  the  fixed  acid  is 
made' with  sufficient  exactitude  by  evaporating  20  cc.  of  the  wine  to  a 
syrupy  consistence,  heating  it  further  for  half  an  hour  to  an  hour  on  a 
water-bath,  subse(piently  treating  it  with  hot  water  and  titrating  after 
it  has  cooled. 
^  "  Zeitsehrift  f.  analyt.  (.'heiuie,"  xxi,  198. 
