AmsepTr'i9i8a nn"  J    Thc  Manufacture  of  Aspirin  Tablets.  645 
from  these  wooden  tubs  should  be  forced  very  quickly  through  per- 
fectly clean  and  well  tinned  screens,  placed  immediately  in  aluminum 
trays,  and  dried  in  vacuo  at  a  temperature  not  exceeding  1200  F. 
It  will  be  found  if  all  these  rules  are  observed  that  aspirin  may 
be  dried  in  three  or  four  hours.'  If  during  this  time  the  aspirin  has 
not  been  exposed  to  the  air  it  will  be  found  that  the  granulation  dry 
and  ready  for  compression  is  in  proper  condition  to  be  placed  on  the 
presses.  No  oil  should  be  added  in  the  running  of  aspirin  tablets,  unless 
absolutely  necessary,  on  account  of  weather  conditions.  It  will  be 
found  that  though  on  account  of  the  absence  of  oil  the  sides  of  the 
tablets  will  not  be  bright  and  polished  (due  to  the  moist  physical 
properties  of  the  ingredients  as  spoken  of  earlier)  the  edges  will  be 
sufficiently  smooth  for  all  purposes ;  and  the  absence  of  the  oil 
(which  would  in  time  penetrate  the  tablet)  will  permit  of  a  harder 
tablet. 
A  minimum  amount  of  pure  white  talcum  not  exceeding  yg  gr. 
to  the  tablet  must  be  used  as  otherwise  picking  on  the  surface  of  the 
tablet  will  occur.  If  the  engraving  of  monogram  punches  is  very 
fine  it  will  be  necessary  to  increase  the  amount  of  talcum  in  order  to 
prevent  the  material  from  sticking  in  the  engraving.  It  should  be 
borne  in  mind  that  talcum  is  objectionable  in  all  cases  and  as  little 
as  possible  should  be  used. 
As  speedy  .disintegration  of  all  tablets  is  considered  essential,  a 
disintegrating  agent  must  be  used.  Doubtless,  known  to  many, 
potato  starch  is  the  disintegrating  agent  par  excellence  as  it  swells 
very  rapidly  and  ruptures  a  tablet  very  quickly  when  it  is  introduced 
into  aqueous  solution. 
The  following  criticisms  in  general  might  be  based  on  the  aspirin 
tablets  at  present  supplied  by  all  except  one  or  two  manufacturers  ; 
that  many  of  them  are  off  color,  some  having  unquestionably  been 
subjected  to  contamination.  Corn  starch  has  been  used  by  many  in 
preference  to  potato  starch,  the  excipient  used  by  some  is  also  too 
heavy  and  too  slow  drying. 
The  nature  of  engraving  used  on  such  monogram  punches  as 
have  been  operated  in  making  aspirin  tablets  is  not  of  a  proper  make 
to  use  on  tablets  of  such  dusty  physical  appearance.  Others  through 
not  using  a  proper  disintegrating  agent  have  compressed  the  tablets 
too  hard,  which  makes  them  too  brittle  for  carrying.  In  other  cases 
to  permit  of  speedy  disintegration  insufficient  pressure  has  been 
applied. 
