Am.  Jour.  Pliarm.  "I 
Sepr.,  1882.  j" 
Analysis  of  Wine. 
445 
Eight  hours.  Ten  hours. 
Current  of  coal  gas,      .       .       .    1"84  per  cent.    1-80  per  cent. 
Current  of  air,  ....       1*90       "  1-86 
The  difference  between  the  resnlts  of  the  two  esthnations  is  probably 
due  to  the  extractive  matter  in  the  one  case  taking  up  oxygen  from 
the  air ;  but  it  is  not  considered  sufficient  to  constitute  an  essentially 
larger  quantitative  result  in  drying  under  access  of  air  than  in  a  current 
of  coal  gas. 
If  the  wine  be  first  evaporated  upon  a  water-bath  in  an  open  pla- 
tinum dish  to  a  syrupy  consistence  it  only  requires  to  be  heated  for 
three  hours  in  the  drying  chest  before  reaching  a  point  where  the  dif- 
ference between  two  weighings  is  dependent  entirely  upon  the  volatility 
of  the  glycerin.  Experiments  made  to  determine  the  extent  of  this 
volatility  showed  that  it  amounted  to  about  10  per  cent,  of  the  glycerin 
present  during  the  evaporation  on  the  water-bath  and  another  4  per 
cent,  in  the  drying  chest.  iSo  that  a  wine  containing  1  per  cent,  of 
glycerin  would  lose  about  0*14  per  cent,  through  its  volatilization 
during  evaporation  and  drying ;  but  in  a  low  wine,  which  with  5  or  () 
per  cent,  of  alcohol  would  probably  contain  only  0*4  2)er  cent,  of  gly- 
cerin, the  loss  would  only  amount  to  ()'05  per  cent.  If,  however,  the 
extract  be  dried  at  110°C.,  experiment  has  shown  that  in  this  part  of 
the  operation  alone,  in  three  hours,  about  10  per  cent,  of  the  glycerin 
present  is  driven  olf,  so  that  at  the  end  of  the  drying  the  total  loss  is 
considerably  larger  than  in  drying  at  100°C. 
Alteration  in  the  other  constituents  of  the  extract  is  relatively  small 
when  the  drying  is  effected  at  lOO^C.  Fifty  cc.  of  wine,  containing 
0'47  total  acids,  was  evaporated  to  the  consistence  of  a  syrup,  then 
heated  further  for  half  an  hour  upon  a  water-bath,  after  which  the  non- 
volatile acid  amounted  to  0"36  per  cent.  The  extract  of  the  same  wine 
after  drying  three  hours  at  100°  showed  upon  titration  0*28  per  cent,  ; 
that  dried  at  110°C.  showed  0.22  per  cent.;  and  that  dried  at  120° 
C.  O'll  per  cent,  of  non-volatile  acid. 
Grete  has  recommended  that  in  order  to  obviate  the  decomposition 
of  the  non-volatile  constituents  of  the  extract  during  drying,  and  espe- 
cially to  entirely  prevent  volatilization  of  glycerin,  the  wine  should  l)e 
evaporated  with  a  measured  quantity  of  titrated  baryta  water.  Some 
experiments  have  b(;en  made  by  the  authors  to  determine  (1)  wliether 
an  indiffer(!nt  body  like  glycerin  actually  enters  into  chemical  com- 
bination with  caustic  l)aryta  so  as  to  be  no  longer  volatile  at  11()°(\; 
