Am.  Jour.  Pharai.  ] 
April,  1883.  / 
Quinium  Salts. 
175 
with  bases  salts.  Tannin  is  the  anhydrate  of  gallic  acid  ;  but  like  many 
other  anhydric  oxides,  it  does  not  generate  the  hydrate  by  direct  con- 
tact with  water.  Similar  to  this  order  of  oxides  it  needs  the  interven- 
tion of  bases  or  either  acids  reinforced  by  a  prolonged  heat  to  induce  a 
combination.  After  the  completion  of  the  reaction  the  product  is  of 
course  gallic  acid,  either  free  or  as  gallate  of  the  base.  Ordinarily^ 
however,  tannin  does  unite  in  a  certain  way  with  bases  as  well  as  acids, 
but  not  by  means  of  what  are  properly  termed  basic  affinities,  the 
resulting  compounds  are  in  no  sense  saline.  They  are  not  gallates, 
neither  are  they  tannates ;  because  gallic  acid  is  not  regenerated  in  this 
reaction,  and  tannic  acid  does  not  exist.  An  acid  oxide  contains  no 
carboxylic  hydrogen,  replaceable  by  basic  radicles,  since  the  anhydrate  is 
itself  an  oxygen  substitution  of  this  hydrogen.  But  in  many  cases  the 
oxide  is  possessed  of  alcoholic  hydroxy  1,  whose  hydrogen  can  be 
replaced  by  other  radicles  under  peculiar  conditions.  The  organic 
acids  are  derivations  of  carbonic  acid,  CO  (OH)2,  by  substituting  other 
radicles  for  a  hydroxyl  group.  Their  basicity  depends  upon  the  num- 
ber of  carboxyls  or  carbonic  acid  residues  CO.  OH,  and  their  atomicity 
upon  the  number  of  hydroxyls,  OH,  contained  within  their  molecule. 
They  may  therefore  be  very  conveniently  termed  mono,  di,  tri,  etc.,. 
carbonic  acids  of  the  saturated  hydrocarbon,  whose  hydrogen  the  car- 
bonic acid  residue  displaces.  Thus  acetic  acid  is  a  methane  carbonic 
acid,  lactic  acid  an  ethane  hydrocarbonic  acid,  tartaric  acid  an  ethane 
dihydro-dicarbonic  acid,  and  citric  acid  a  propane  hydro-dicarbonic 
acid.  Gallic  acid  is  a  benzene  trihydrocarbonic  acid,  Cg  Hg  (OH)3, 
•CO.OH,and  is  therefore  tetratomic  and  monobasic,  its  anhydrate  being 
2(C6H2  (OH)3  CO).  O,  hence  contains  six  alcoholic  hydroxyls,  whose 
hydrogen  is  replaceable  by  other  radicles.  The  resulting  compounds 
may  properly  be  styled  alcoholates  and  therefore  the  coalescenses  of 
tannin  with  other  molecules  through  the  medium  of  its  alcoholic 
hydroxyl  are  correctly  termed  tannolates.  Tannin  has  a  varied 
affinity  for  many  substances,  and  in  different  degrees  for  the  same 
body.  It  has  a  great  propensity  for  combining  with  acids  and  neutral 
salts,  though  with  some,  as,  for  instance,  acetic  acid,  it  does  not  unite. 
By  reason  of  this  peculiarity  the  quinium  tannolate,  as  ordinarily  pre- 
pared, contains  a  very  large  excess  of  tannin  compounded  with  free 
acid,  so  as  to  constitute  the  article  in  reality  a  mixture.  Manufac- 
turers indeed  endeavor  to  have  the  largest  possible  amount  of  tannin 
absorbed,  deeming  such  a  procedure  perfectly  legitimate,  in  view  of 
