AMseJpU!;iP874RM,j         Reaction  of  Gallic  Acid.  429 
NOTE  ON  PROCTER'S  REACTION  OF  GALLIC  ACID. 
By  Professor  Fluckiger. 
In  this  journal,*  it  is  stated  that  a  mixture  of  faintly  alkaline 
arseniate  and  gallic  acid  in  aqueous  solution  by  absorption  of  oxygen 
■developes  a  green  color. 
There  can  be  no  doubt  as  to  the  correctness  of  the  fact.  I  wish 
only  to  point  out  that  the  arseniate,  that  is  to  say,  arsenic  acid,  has 
nothing  whatever  to  do  with  this  reaction.  The  phosphates,  borates, 
silicates,  carbonates,  etc.,  may  quite  as  well  be  used  instead  of  the 
arseniate.  The  cause  of  the  green  reaction  is  the  presence  of  a 
trifling  amount  of  alkali,  a  fact  which  has  long  been  well-known  and 
expressly  recorded,  for  instance,  in  Gmelin's  **  Organic  Chemistry," 
among  other  reactions  of  gallic  acid.  The  reaction  is  developed  by 
any  alkali,  caustic  or  not,  provided  it  be  present  in  but  extremely 
small  quantity.  Thus  bicarbonate  of  sodium  is  a  very  convenient 
means  of  showing  the  reaction  under  notice ;  it  displays,  it  need 
scarcely  be  mentioned,  but  a  very  moderate  alkaline  reaction. 
The  green  reaction,  it  will  be  observed,  has  its  merit,  as  it  is  not 
produced  either  by  gallotannic  acid  or  by  pyrogallol. 
There  is  another  reaction  which  likewise  is  sufficient  to  distinguish 
gallic  acid.  If  to  an  aqueous  solution  of  gallic  acid  some  drops  of  a 
dilute  solution  of  ferrous  sulphate  (about  one  part  of  vitrol  in  100 
of  water)  are  added,  the  mixture  remains  for  some  time  colorless, 
provided  the  gallic  acid  be  free  from  tannic  acid,  and  the  ferrous  salt 
from  ferric  ;  the  solutions,  moreover,  ought  to  be  made  in  the  very 
moment  they  are  to  be  used,  Ferrous  gallate  is  of  an  intense  violet 
hue;  but  it  is  not  produced  in  the  above  mixture,  because  the  solution 
of  the  sulphate  has  an  acid  reaction.  This  is  due  to  sulphuric  acid, 
which  can  be  superceded  by  acetic  acid  if  we  add  a  little  acetate  of 
sodium.  Then  a  trace  of  acetic  acid  is  set  free,  and  this  now  is  not 
able  to  prevent  the  development  of  the  violet  color  of  ferrous  gallate  ; 
an  intense  violet  instantly  makes  its  appearance. — Pharm.  Journal 
and  Trans.  [London)  August,  1874. 
A  NEW  REMEDY  FOR  HAY  FEVER  AND  SNEEZING. 
By  Horace  Dobell,  M.  D. 
Senior  Physician  to  the  Royal  Hospital  for  Diseases  of  the  Chest. 
At  this  season  of  the  year,  when  "  sneezers  "  and  sufferers  from 
"  hay  fever"  are  in  the  depths  of  their  miseries,  it  is  merciful  to  make 
*  Airier.  Journal  of  Pharmacy,  August,  1874,  p.  373. 
