Am  Jour.  Pharm. 
Nov.,  1889. 
Physiology  of  Tannin. 
567 
SOLUBILITY  OF  SUGAR  IN  WATER.1 
By  L.  Perier. 
Every  specimen  of  crystallized  sugar  has  its  own  specific  coefficient 
of  solubility,  but  with  all  specimens,  at  a  given  temperature,  the  solu- 
tion of  each  additional  gram  in  100  cc.  increases  the  specific  gravity 
by  a  constant  amount  for  all  concentrations  between  1  per  cent,  and 
40  per  cent.  Above  45  per  cent,  the  increase  is  somewhat  less  regular, 
the  difference  between  two  consecutive  terms  gradually  becoming 
smaller.  It  is,  however,  easy  to  construct  tables  from  1  per  cent,  to 
40  per  cent.,  and  from  55  to  100,  by  taking  in  each  series  terms  which 
are  not  far  removed  from  one  another. 
The  strength  of  the  solution  can  be  calculated  from  the  specific 
gravity  and  vice  versa,  and  the  result  is  accurate  to  the  third  decimal 
place.  The  calculation  is  based  on  the  specific  gravity  of  a  10  per 
cent,  or  50  per  cent,  solution.  If  S10  is  the  specific  gravity  of  a  10 
per  cent,  solution,  W  the  percentage  strength  of  the  solution  in  ques- 
tion, and  S^  the  required  specific  gravity, 
The  reverse  operation  gives  the  percentage  strength  from  the  spe- 
cific gravity. 
When  sugar  is  rapidly  dissolved,  especially  with  sugar-candy,  there 
is  a  notable  development  of  heat,  which  cannot  be  attributed  to  the 
formation  of  hydrates,  and  is  probably  due  to  internal  friction. 
Glucose  behaves  in  the  same  way  as  saccharose,  and  hence  the  spe- 
cific gravity  may  be  used  with  advantage  for  determining  the  strength 
of  its  solutions. 
PHYSIOLOGY  OF  TANNIN.2 
By  G.  Kraus. 
The  formation  of  tannin  in  leaves  depends  on  the  presence  of  light 
and  carbonic  anhydride  :  the  outer  leaves  of  a  plant  exposed  to  direct 
sunlight  will  contain  far  more  tannin  than  the  inner  leaves.  Leaves 
which  are  not  green  are  not  capable  of  producing  tannin.  It  must 
not,  however,  be  assumed  that  tannin  is  a  product  of  assimilation  of 
the  chlorophyll-grains,  inasmuch  as  there  are  innumerable  plants 
1  Compt.  rend.,  cviii,  1202—1204 ;  from  Jour.  Chem.  Soc,  1889,  p.  846. 
2  Bied.  Centr.,  xviii,  330  ;  reprinted  from  Jour.  Chem.  Soc,  Sept.,  1889,  p.  917, 
