ON  T ANNATE  OF  ALUMINA. 
25 
ON  TANNATE  OF  ALUMINA. 
By  William  Procter,  Jr. 
The  London  Medical  Gazette  contains  an  article  on  the  medi- 
cal application  of  Tannate  of  Alumina,  in  which  it  is  stated  that 
Mr.  Rogers  Harrison  had  prepared  a  combination  of  alumina  and 
tannic  acid  which  "was  of  a  dirty  yellowish  color,  and  in  crys- 
tals about  the  size  of  those  of  coarse  sugar,  and  readily  soluble 
in  hot  water."  It  had  been  used  successfully  for  inflammation 
of  the  urethral  passages  in  the  form  of  injection,  two  to  ten 
grains  of  the  salt,  according  to  circumstances,  dissolved  in  suffi- 
cient distilled  water. 
Having  recently  received  a  prescription  for  ten  grains  of  this 
salt  dissolved  in  two  fluid  ounces  of  water,  and  being  unable  in 
any  of  a  number  of  chemical  works  at  my  command,  to  find  any 
account  of  the  salt,  I  undertook  to  make  it,  but  could  not  succeed 
in  obtaining  a  soluble  compound  of  tannic  acid  and  alumina 
that  answered  to  the  description  of  that  of  Mr.  Harrison,  all  of 
them  being  insoluble  or  nearly  so  in  water,  and  entirely  amor- 
phous. 
1st.  An  equivalent  of  tannic  acid  was  triturated  with  one  of 
alumina  in  the  pulpy  hydrated  condition  ;  combination  ensued, 
and  an  insoluble  or  slightly  soluble  compound  resulted.  The 
same  result  occurred  when  two  and  three  equivalents  of  alumina 
were  employed.  When  agitated  with  water  after  standing  in  a 
pulpy  state  for  several  weeks,  and  the  water  filtered  off,  the  latter 
gave  no  evidence  of  tannic  acid  or  a  soluble  tannate. 
2d.  A  solution  of  alum  in  water  was  prepared,  containing  37 
grains  to  the  fluid  ounce,  which  quantity  contains  four  grains  of 
anhydrous  alumina.  A  solution  of  tannic  acid  in  water  was  then 
made,  containing  16  grains  to  the  fluid  ounce.  The  alumina  and 
tannic  acid  existed  nearly  in  the  proportion  of  their  equivalents 
in  these  solutions. 
Equal  measures  were  mixed  together  without  any  precipitation, 
showing  that  free  tannic  acid  is  unable  to  displace  alumina  from 
its  combination  with  sulphuric  acid,  notwithstanding  the  insolu- 
bility of  the  aluminous  tannate,  even  when  they  are  boiled. 
3d.  When,  however,  ammonia  is  carefu  ly  added  to  a  fluid 
o 
O 
