600  Estimation  of  Tannin.  { '^'"Dec"'i?8r'"" 
little  more  glycocholic  acid  than  can  be  dissolved  by  the  taurocholic 
acid  set  free  on  the  addition  of  acid. 
Solubility  of  Glycocholic  Acid. 
In  water — 
Temperature  of  water                                 20°         60°  80°  100° 
Glycocholic  acid  dissolved  (per  cent.)          0*033      0*102  0-235  0-85 
In  alcohol- 
Strength  of  alcohol  (per  cent.)    1  2         10         20        30  50 
Acid  dissolved  (per  cent.)         ()'035     0-049     O'lO     0-275     1-674  27-53 
In  taurocholic  acid  — 
Strength  of  solution  employed  (per  cent.)  1  5  10 
Glycocholic  acid  per  cent,  dissolved   0-056        0-37  0-69 
Ether,  benzene,  and  chloroform  at  20°C.  dissolve  respectively  0*093, 
0*009,  and  0*011  per  cent,  of  glycocholic  acid. 
Strecker  observes  Handworterbuch,"  2,  1192)  that  glycocholic 
acid  melts  above  100°,  giving  off  water  and  forming  glycocholonic 
acid.  The  author  finds  the  melting  point  always  constant  at  132  to 
134°,  but  has  not  remarked  the  loss  of  3*9  per  cent.  (1  mol.)  of  water 
necessary  for  the  above  change.  At  100  to  115°  the  loss  in  weight  is 
insignificant ;  at  140  to  150°,  after  eight  hours,  it  is  2*6  per  cent. ;  at 
160  to  170°,  after  two  hours,  it  is  4*5  per  cent.  When  a  saturated 
solution  of  pure  glycocholic  acid  is  boiled  with  water  for  24  hours, 
about  22  per  cent,  is  converted  into  paraglycocholic  acid.  This  acid 
(m.  p.  183  to  184°)  is  nearly  insoluble  in  water;  the  solution  shows 
no  reaction  wath  litmus,  and  is  tasteless,  although  the  acid  itself  is 
intensely  bitter.  The  dry  substance  adheres  strongly  to  glass,  and 
appears  to  be  a  very  bad  conductor  of  electricity.  Titration  with  soda 
(the  glycocholates  are  neutral)  proves  that  glycocholic  acid  is  mono- 
basic.— Jour.  Chem.  Soc,  Nov.,  1882;  from  Manatsh.  Chem.,  3,  325- 
342. 
ESTIMATION  OF  TANNIN. 
By  F.  Simand. 
The  author  had  occasion  to  make  a  number  of  tannin  estimations 
according  to  LowenthaFs  improved  method,  and  found  that  the  per- 
centage of  tannin  in  the  same  material  was  subject  to  certain  variations, 
higher  results  being  obtained  when  a  larger  quantity  of  material  was 
boiled  out.    A  series  of  experiments  was  therefore  made,  the  object 
