264 
IMPURITIES  IN  GLYCERIN. 
BLUE-BLACK  WRITING  INK. 
A  correspondent  has  sent  us  the  following  recipe  for  a  blue- 
black  writing-ink,  which,  he  says,  answers  very  well  for  a 
copying-ink : — 
Take  of  Aleppo  Galls,  bruised    .       .       .    5J  ounces. 
Cloves,  bruised     ....      J  ounce. 
Sulphate  of  Iron  .       .       .    1J  " 
Sulphate  of  Indigo,  in  the  form  of  a 
slightly-acid  paste  (Sulphindylate 
of  Potash?)       .       .       .  .14" 
Sulphuric  Acid      .       .       .       .85  minims. 
Rain  Water,  cold  .  .  .  .  40  ounces. 
Macerate  the  galls  and  cloves  in  20  ounces  of  the  water  for  a 
week  \  decant  the  liquor,  and  add  to  the  residue  of  the  solid  in- 
gredients 10  ounces  of  the  water,  with  which  continue  the  mace- 
ration for  four  days ;  then  decant  as  before,  and  repeat  the  ma- 
ceration with  the  remaining  10  ounces  of  water  for  another  period 
of  four  days.  Mix  now  the  whole  of  the  liquors,  recovering 
from  the  galls  all  that  can  be  obtained  by  squeezing  them  in  a 
cloth,  and  afterwards  filter.  To  this  add  first  the  sulphate  of 
iron,  then  the  sulphuric  acid,  and  lastly  the  indigo  paste.  Care 
must  be  taken  that  the  indigo  does  not  contain  much  free  acid. — 
Lond.  Pharm.  Journ.,  March,  1868. 
IMPURITIES  IN  GLYCERIN. 
To  the  Editor  of  the  Chemical  News. 
Sir, — The  writer  of  the  article  on  glycerin  in  Kunst  and 
G-eiveberblatt  is  correct  in  attributing  the  acrid,  irritating  proper- 
ties of  some  glycerin  to  the  mode  of  preparation  ;  but  I  have 
distilled  glycerin  which  was  quite  as  unsuitable  for  medicinal 
or  surgical  purposes  as  any  spoken  of.  The  volatile  fatty  acids 
and  ethers,  which  exist  in  crude  glycerin,  are  sometimes  con- 
densed with  the  glycerin,  and  these  have  very  irritating  proper- 
ties. 
In  the  glycerin  which  is  made  without  distillation,  the  volatile 
acids,  and  ethers  exist,  but  not  in  the  same  state  as  after  distil- 
