74 
Pills  and  Pill  Coatings. 
Am.  Jour.  Pharm. 
Feb.,  1878. 
Sometimes  the  ingredients  of  a  formula  will,  when  mixed,  them- 
selves form  a  mass  suitable  for  dividing  into  pills  ;  but  usually  an  excip- 
ient  has  to  be  added,  and  the  proper  selection  of  a  suitable  one  consti- 
tutes the  chief  art  in  pill  making.  The  list  of  excipients  is  somewhat 
lengthy  in  detail,  but  they  may  be  summarized  as  follows  :  Glycerin 
of  tragacanth,  glycerin,  treacle,  syrup,  mucilage,  tinctures,  spirit,  water, 
confections,  extracts  ;  powders  of  tragacanth,  gum  arabic,  taraxacum 
root,  bees'-wax,  almond  meal,  soap,  bread  crumb,  etc.  Mr.  Martin- 
dale  has  recommended  a  mixture  of  starch  and  glycerin,  and  Mr. 
Walter  Searle  a  solution  of  soluble  cream  of  tartar  and  citrate  of 
potassa,  to  which  is  added  syrup  and  mucilage.  Whatever  be  the  in- 
gredients or  the  excipients,  it  should  be  borne  in  mind  that  to  attain 
satisfactory  results  a  pill  must  resemble  a  building  and  contain  constit- 
uents possessing  the  physical  characteristics  of  both  bricks  and  mortar  ; 
these  too,  if  possible,  in  such  proportions  as  to  produce  a  substantial 
structure. 
Of  the  soft  or  plastic  excipients  in  the  foregoing  list,  glycerin  of 
tragacanth  is  probably  the  most  generally  useful,  as  by  means  of  it  in 
small  quantity  we  are  enabled  to  get  sufficient  adhesiveness  to  bring 
solid  particles,  themselves  devoid  of  that  property,  into  a  compact  mass,, 
and  cause  them  to  cohere  firmly  together  without  imparting  undue 
hardness  or  insolubility.  Metallic  oxides  and  salts  are  by  it  rendered 
most  tractable,  and  a  pill  which  would  otherwise  be  very  large  is  by  it 
rendered  quite  within  the  average  size.  I  produce  samples  of  pills 
containing  five  grains  bromide  of  potassium,  and  ten  grains  of  subni- 
trate  of  bismuth  respectively,  neither  of  which  are  larger  then  a  five 
grain  colocynth  pill.  Glycerin  itself,  except  in  very  small  quantity,  is 
not  a  good  excipient  though  frequently  prescribed  ;  pills  containing  it 
are  liable  to  absorb  moisture  and  become  sticky  ;  they  also  do  not  take 
silver  well  when  required  so  to  do.  Pills  prepared  with  mucilage  are 
liable  to  become  very  hard  when  kept  for  any  length  of  time  ;  with 
spirit  they  require  to  be  rolled  off  quickly  or  will  become  brittle  and 
crumble  on  the  machine.  Spirit  should  never  be  used  when  there  is 
much  resin  in  the  pill,  indeed  with  this,  as  with  the  other  liquid  excip- 
ients named,  most  pharmacists  will  have  ascertained  the  special  cases  to 
which  they  are  best  adapted  as  the  result  of  experience.  Of  the  ex- 
tracts that  of  liquorice  is  about  the  most  useful,  as  it  possesses  no 
active  medicinal  properties  *  confection  of  roses  and  that  of  hips  usually 
