116 
ON  aLYCERATE  OF  TAR. 
Rub  the  tar  in  a  mortar,  first  with  the  carb.  magnesia  gradually 
added,  until  a  smooth  pulverulent  mixture  is  obtained  ;  then 
gradually  add,  in  small  portions  at  a  time,  with  thorough  tritu- 
ration continued  for  fifteen  or  twenty  minutes,  six  fluidounces 
of  the  mixture  of  alcohol,  glycerin  and  water  and  strain,  with 
strong  expression  ;  return  the  residue  to  the  mortar,  and  repeat 
the  trituration  as  before,  with  five  fluidounces  more  of  the  same 
liquid,  and  express  ;  again  treat  the  dregs  in  same  manner  with 
the  remainder  of  the  menstruum,  and  after  expression  reduce  the 
residue  by  trituration  to  a  uniform  condition,  and  finally  pack 
firmly  in  a  glass  funnel  prepared  for  percolation,  and  pour  upon 
it  the  expressed  liquors,  previously  mixed,  and  when  the  mixture 
has  all  passed  from  the  surface,  continue  the  percolation  with 
water  until  one  pint  of  liquid  has  been  obtained. 
It  will  be  observed  that  the  manipulation  employed  above  is 
similar  to  that  adopted  by  the  writer  in  the  preparation  of  the 
syrup  of  tar,  the  formula  for  which  will  be  found  in  the  January 
number  of  this  Journal.  The  percolation  is  well  calculated  to 
exhaust  the  tar  of  all  that  is  medicinally  valuable. 
When  first  prepared,  the  "  Glycerate  is  of  a  beautiful  rich 
reddish-brown  color.  After  a  short  time  it  looses,  in  a  measure, 
its  transparency  in  consequence  of  a  separation  of  inert  pitchy 
matter.  But  its  pristine  beauty  may  be  easily  restored  by  filtra- 
tion, which  is  accomplished  in  a  few  minutes,  as  it  passes  the 
filter  very  rapidly.  This  deposit  of  resinous  matter  continues 
for  a  considerable  lapse  of  time,  but  does  not  diminish  or  impair 
in  the  slightest  degree  the  medicinal  virtues  of  the  preparation, 
but  simply  temporarily  mars  its  beauty. 
It  possesses  in  a  high  degree  all  the  sensible  properties  of 
tar.  In  this  they  are  more  strongly  marked  than  in  any  prepa- 
ration of  tar,  excepting  the  tincture,  I  have  seen. 
In  conjunction  with  the  fluid  extract  of  wild-cherry  bark, 
acetate,  or  syr.  squills,  syrups  of  sanguinaria,  lactucarium,  &c., 
in  varied  proportions  to  suit  the  views  of  the  prescriber,  it  will 
form  elegant  and  palatable  combinations,  which  will  be  found 
peculiarily  adapted  to  the  treatment  of  chronic  coughs,  and  the 
various  diseases  of  the  pulmonary  organs. 
Each  fluidounce  of  the  glycerate,  if  the  process  has  been  care- 
