CHEMICAL  COMPOUND  OF  TANNIC  ACID,  ETC.  207 
Under  the  microscope  the  crystals  appear  to  be  of  different 
forms,  some  being  prisms,  others  pyramids,  and  some  in  the 
shape  of  a  cross.  They  all  reflect  the  light  very  brightly,  ap- 
pearing like  stars,  although  viewed  by  diffused  light. 
I  have  also  observed  a  precipitate,  having  the  same  characters, 
in  fennel  water,  and  as  the  solid  constituents,  or  steareoptenes, 
of  these  oils  are  identical  in  composition,  I  have  arrived  at  the 
conclusion  that  the  crystalline  substance  consists  of  an  acid  in 
combination  with  magnesia,  which  acid  is  probably  formed  by 
the  oxidation  of  the  steareoptene,  in  consequence  of  its  minute 
division  in  contact  with  the  water  and  magnesia. 
NOTE  ON  THE  SUPPOSED  CHEMICAL  COMPOUND  OF  TANNIC 
ACID,  ETHER  AND  WATER. 
By  Edward  Parrish. 
In  justice  to  my  colleague,  J.  M.  Maisch,  I  desire  to  call  at- 
tention to  an  observation  of  his,  made  previously  to  the  recent  pa- 
per of  Professor  Bolley,  noticed  in  the  current  number  of  this 
Journal,  taken,  from  Annalen  der  Chem.  und  Pharm.,  July, 
1860.  In  the  second  edition  of  my  "  Introduction  to  Prac- 
tical Pharmacy,"  published  at  the  close  of  the  year  1858,  the 
following  remark  from  his  pen  occurs  under  the  head  of  Tannic 
Acid : 
"  The  concentrated  ethereal  solution  contains  46.5  to  56.2 
per  cent,  of  tannic  acid  (Mohr),  and  is  insoluble  in  ether.  Could 
this  be  a  chemical  compound  between  oxide  of  ethyle  and  tannic 
acid?  Thirteen  equivalents  of  the  former  =  481,  to  one  equiva- 
lent of  the  latter  =618,  require  exactly  56«2  per  cent,  of  tan- 
nin and  43-8  per  cent,  of  ether." 
The  experiments  of  Bolley  seem  to  add  an  additional  argu- 
ment for  this  view  of  the  composition  of  the  very  peculiar 
etherole  of  tannin,  and  render  its  numerical  relations,  as  above 
expressed,  still  more  interesting.  Until  the  subject  is  further 
investigated,  however,  the  supposed  "  Tannate  of  Ether  and 
Water  "  must  be  held  in  abeyance;  a  demonstration  of  its  exist- 
ence and  composition  being  placed  among  our  chemical  de- 
siderata. 
