PHARMACEUTICAL  GLEANINGS  AND  NOTICES.  325 
sieves  of  the  sizes  of  12,  15,  and  20  meshes  to  the  linear  inch, 
and  these  are  to  be  fitted  together  like  a  drum  sieve,  the  coarsest 
being  at  the  top,  the  finest  at  the  bottom.  The  mass  is  now 
rubbed  through  the  top  sieve  with  the  open  hand,  the  sieves  are 
then  shaken  as  in  ordinary  sifting.  The  second  sieve  will  retain 
the  larger  granules,  the  lower  sieve  the  finer,  whilst  the  pul- 
verulent particles  pass  through  below,  and  may  again  be  treated 
after  being  damped  in  the  manner  as  before.  When  the  mass 
is  formed  into  cakes  and  bruised,  it  is  sifted  in  the  same  way, 
the  finest  particles  being  worked  over  again. 
3.  Drying,  Coating,  and  Water  Proofing  the  Granules. — 
The  granules  by  the  first  process  are  spread  on  paper  and  occa- 
sionally stirred  till  dry,  or  if  the  process  is  not  injurious  to  some 
ingredient  they  may  be  dried  in  a  metallic  pan  subjected  to  a 
moderate  heat,  with  constant  stirring,  or  more  speedily  in  a  cur- 
rent of  dry  hot  air  with  occasional  stirring.  When  perfectly 
dry  they  are  placed  in  a  mortar,  or  capsule  of  convenient  size 
and  a  sufficient  quantity  of  strong  tincture  of  tolu  (3iij.  to 
f.^j.)  in  which  any  flavor  desired  has  been  dissolved  and  stirred 
until  the  entire  mass  of  granules  appear  to  be  equally  coated  and 
glossy,  when  they  are  again  subjected  to  the  drying  process  with 
constant  stirring. 
Granules  well  prepared  in  this  manner  are  compact,  and  to 
some  extent  insoluble  in  cold  water  ;  a  desideratum,  as  they  may 
be  conveniently  administered  in  that  vehicle,  without  imparting 
to  the  water  the  slightest  taste,  smell,  or  color.  The  proportion 
of  gum  in  these  granules  on  an  average  is  one-sixteenth,  and 
that  of  the  tolu  too  small  to  estimate,  so  that  in  calculating 
doses,  but  little  abatement  need  be  made  for  these  excipients. 
Advantages  of  Granulation. — This  form  tends  to  preserve 
medicines  containing  volatile  active  principles.  With  the  excep- 
tion of  extracts,  granules  contain  a  larger  percentage  of  active 
matter  than  most  other  preparations  of  drugs,  and  for  this 
reason  many  saline  and  caustic  irritant  remedies  should  not 
be  exhibited  in  this  form,  that  of  solution  being  more  appro- 
priate. 
Again,  as  all  the  officinal  pill  masses  are  capable  of  being  as 
.easily  granulated  as  powders,  it  is  not  improbable  that  pills  may 
be  to  some  extent  superseded  by  granules.     The  granulation 
