ON  GLUCOSE. 
415 
vinous  character  to  the  beer.  When  the  latter  object  is  not  in  view  the 
best  substitute  for  barley  will  always  be  found  in  maize  or  some  other 
cheap  grain. 
"  Not  so  in  the  manufacture  of  wine.  For  this  purpose,  good  starch 
sugar,  containing  not  exceeding  15  per  cent,  of  dextrine,  is  decidedly 
preferable  to  cane  sugar.  A  pound  of  the  latter  of  the  quality  suitable 
for  wine  manufacture,  costs  at  least  15  cent;  whereas,  as  just  stated, 
good  starch  sugar  from  maize  can  be  sold  at  8  cents.  Now  as  5  lbs.  of 
starch  sugar  are  equivalent  to  4  lbs,  of  cane  sugar  as  regards  their  yield 
of  alcohol,  the  balance  is  altogether  in  favor  of  maize  sugar,  to  wit  : 
4  lbs.  cane  sugar  at  15  cents       .       .       .       .60  cents. 
5  lbs.  grape  sugar  at  8  cents        .       .       .       .40  cents. 
"  The  15  per  cent,  of  dextrine  (gum)  contained  in  the  maize  sugar  will 
(according  to  the  usual  proportion  of  sugar  added  to  must)  increase  the 
amount  of  '  extract '  in  wine  only  by  a  few  per  cent.,  and  will  tend  to  give 
it  the  *  monthly  '  taste  (body)  which  in  meager  wines,  already  fermented, 
is  sought  to  be  produced  by  the  addition  of  glycerine. 
"  Enormous  quantities  of  cane  sugar  are  already  Ijeing  consumed  in  the 
wine  manufacture  in  this  country;  so  that  even  as  a  consideration  of  na- 
tional economy  it  is  highly  important  to  supply  in  maize  sugar  a  partial 
substitute  for  imported  cane  sugar." 
In  France  there  is  a  use  for  grape  sugar  arising  from  the  fact 
that  the  sugar  manufacturers  do  not  prepare  molasses  ready  for 
the  market  as  they  do  in  this  country.  The  crude  molasses  is 
bought  up  by  second  parties  and  the  grape  sugar  is  used  very 
largely  by  them  to  extend  it  and  give  it  body.  An  alkaline  so- 
lution of  grape  sugar  is  converted  by  heat  into  a  dark  brown 
body,  called  melassic  acid.  This  acid  has  a  powerful  affinity  for 
oxygen,  and  reduces  the  Cu  0  to  Cu  2  0.  Some  of  the  tests  for 
grape  sugar  are  founded  upon  this  re-action.  One  of  them, 
known  as  Fehling's  test,  is  prepared  as  follows  :  A  standard 
copper  solution  is  made  from  1  oz.  crystallized  sulphate  of  cop- 
per, 3  ozs.  cream  of  tartar,  IJ  ozs.  pure  carbonate  of  potash,  14 
or  16  ozs.  of  a  solution  of  caustic  soda,  (sp.  gr.  1.12,)  and  water 
until  the  solution  measures  15,160  water  grains;  200  measured 
grains  of  this  solution  contain  a  quantity  of  copper  that  would 
be  reduced  by  1  grain  of  sugar,  each  atom  of  sugar  reducing  10 
atoms  of  the  black  oxide  of  copper  to  the  state  of  suboxide. 
Cane  sugar  is  converted  into  grape  by  boiling  with  weak  sul- 
phuric acid,  and  it  can  then  be  easily  tested  by  the  standard  so- 
lution. It  sometimes  becomes  necessary  to  test  for  sugar  in 
diabetic  urine  ;  this  is  accomplished  in  various  ways.    One  of 
