182 
Glycerinum  Acidi  Gallici. 
/Am.  Jour.  Pharm. 
I      April,  1889. 
the  solution  containing  one  of  them  chlorine  water  and  then  ammonia, 
a  beautiful  red  color  being  at  once  produced.  With  tannic  acid  the 
color  is  very  well  marked  and  distinct,  but  is  not  quite  so  noticeable 
with  gallic  acid,  for  with  this  acid,  as  is  known,  ammonia  alone  gives 
a  red  color.  With  a  mixture  of  potassic  ferri-cyanide  and  ammonia 
both  acids  also  give  a  dark  red  colored  solution.  In  the  case  of  tannic 
acid  1  part  in  10,000  of  water  gives  a  distinct  red  color  to  the  whole 
of  the  solution.  In  a  weaker  solution,  say  1  part  in  30,000  of  water, 
the  red  color  is  best  seen  by  looking  down  the  test-tube  through  the 
whole  column  of  the  liquid.  In  still  more  dilute  solutions,  containing 
only  1  part  tannic  acid  in  100,000  of  water,  it  is  better  to  compare 
the  tint,  which  is  now  more  of  a  yellowish  brown,  with  the  tint  of  a 
blank  experiment,  i.  e.,  one  containing  the  same  amount  of  ammonia 
and  of  potassic  ferricyanide  in  the  same  volume  of  water,  but  with  no 
tannic  acid  present.  Under  these  conditions  the  change  in  color  will 
be  perfectly  apparent,  and  the  delicacy  or  the  reaction  may  be  carried 
considerably  further.  The  red  coloring  matter  can  be  salted  out,  and 
I  am  at  present  engaged  on  some  further  investigations  into  its  com- 
position and  properties. —  Chemical  News,  Feb.  1,  p.  52. 
University  College,  Liverpool. 
■  NOTE  ON  GLYCERINUM  ACIDI  GALLICI. 
By  G.  Melvin. 
A  short  time  ago  I  had  occasion  to  dispense  the  following  mix- 
ture : — 
R    Glycerin,  acid,  gallic   ^i. 
Acid,  sulph.  dil     gii. 
Ext.  ergotse  liq   ^  ss. 
Aq.  cinnamomi  ad  ^viii 
Misce. 
It  was  sent  out  a  perfectly  bright  mixture,  but  was  returned  a 
few  hours  afterwards  with  a  message  that  some  mistake  must  have 
been  made.  The  gallic  acid  had  separated  in  bundles  of  large  acicu- 
lar  crystals.  It  was  stated  that  the  mixture  had  been  previously  dis- 
pensed at  different  pharmacies  and  had  never  shown  the  same  separa- 
tion of  crystals  before.  The  mixture  was  again  dispensed  with  a  pre- 
cisely similar  result,  and  to  obviate  the  difficulty  an  additional  half 
ounce  of  glycerin  was  added  to  it  and  sufficed  to  keep  the  acid  in 
