450 
Analysis  of  Wine. 
f  Am.  Jonr.  Pliarui. 
(     Sept.,  1882. 
210  cc.  of  wine,  after  tlie  addition  of  a  few  drops  of  concentrated 
solution  of  potassium  acetate,  is  evaporated  to  a  thin  syrup,  treated 
Avith  90°  alcohol,  the  alcoholic  solution  decanted  when  perfectly  cleai* 
or  filtered,  water  added,  and  the  liquid  decolorized  with  animal  char- 
<*oal,  evaporated  to  about  15  cc,  filtered,  the  filter  washed  and  the 
filtrate  brought  u])  to  30  cc.  (one-seventh  of  the  original  volume  of 
the  wine)  and  polarized.  If  the  resulting  liquid  shows  a  rotation  of 
more  than  0'6°  (AVild)  the  wine  may  be  considered  with  certainty  to 
•contain  potato  sugar. 
If  a  wine  contain  non-inverted  and  unfermented  cane  sugar,  which 
Avould  probably  have  been  added  to  it  after  fermentation  to  increase 
the  amount  of  extract,  the  dextrogyre  action  of  such  a  wine  would  be 
■changed  into  a  levogyre  action  during  the  evaporation  even  by  the 
influence  of  the  natural  acids,  but  more  certainly  if  a  few  drops  of 
hydrochloric  acid  be  added.  The  presence  of  unfermented  cane  sugar 
would  therefore  be  indicated  when  a  wine  first  shows  a  dextrogyre 
action  and  then  after  evapoi^ation  with  hydrochloric  acid  shows  a  cor- 
responding levogyre  action. 
A  6*5  per  cent,  solution  of  cane  sugar,  which  rotated  8*4°  to  the 
right,  was  heated  in  a  water-bath  during  three-quarters  of  an  hour 
with  some  hydrochloric  a(;id,  brought  to  its  original  volume  and  polar- 
ized, when  it  showed  a  left-handed  rotation  of  2*2°.  In  order  to  test 
whether  the  inversion  was  quite  completed,  this  solution  was  now  kept 
ill  active  ebullition  for  half  an  hour,  evaporated  water  being  restored 
as  far  as  possible ;  it  had  then  ac(piired,  without  any  perceptible,  char- 
ring, a  wine  yellow  color,  and  having  been  brought  to  its  original 
volume,  showed  a  lefi-handed  rotation  of  1*7°.  A  sugar  determination 
with  Fehling's  solution  gave  5  per  cent,  of  invert  sugar.  It  follows 
that  a  1  per  cent,  aqueous  solution  of  invert  sugar  rotates  about  0*34°  to 
the  left(l  per  cent,  cane-sugar  solution  rotates  about  1*3°  to  the  right); 
that  the  inversion  of  a  tolerably  large  amount  of  sugar  is  completely 
effected  in  three-quarters  of  an  hour  on  the  water-bath  ;  and  that  by 
longer  heating  to  a  little  over  100°C.  (/.  e.,  to  the  boiling  point  of  the 
sugar  solution)  a  portion  of  tlie  resulting  invert  sugar  is  again  decom- 
posed. When  small  quantities  of  cane  sugar  are  present  the  natural 
acids  of  the  wine  are  sufficient  to  eflect  complete  inversion  during  heat- 
ing ;  but  with  larger  quantities  (i  per  cent,  and  upwards)  it  must  be 
assisted  by  a  little  hydrochloric  acid.    As  soon  as  cane  sugar  in  wine 
