388 
Disintegration  of  Tablets. 
f  aid.  .lour.  Phiirm. 
(      August,  1908. 
disintegration  could  only  be  attributed  to  the  boric  acid,  although 
that  is,  by  comparison,  almost  insoluble. 
At  another  time,  tablets  of  ammonium  chloride  were  being  pre- 
pared. While  this  salt  usually  requires  no  lubricant,  the  weather 
was  exceedingly  damp,  and  it  became  necessary  to  add  a  small  per- 
centage of  talcum  to  overcome  sticking.  A  test  of  these  tablets 
made  on  the  same  machine,  without  readjustment,  before  and  after 
adding  the  talcum,  showed  the  latter  to  be  quicker  in  breaking 
down. 
In  the  above  cases  the  additions  of  material  have  been  of  a  more 
or  less  insoluble  substance  to  a  soluble  substance  forming  the  body 
of  the  tablet,  but  the  reverse  gives  the  same  result.  A  veterinary 
tablet  of  arsenic  trioxide  one  grain  with  cane  sugar  one  grain,  dis- 
integrates, so  rapidly  when  dropped  into  warm  water  that  observ- 
ers have  declared  it  to  be  made  of  an  effervescent  base.  A  tablet 
containing  two  grains  of  cane  sugar  only,  dissolves  but  slowly. 
Quinine  sulphate  with  25  per  cent,  cane  sugar  gives  the  same  result, 
although  neither  quinine  sulphate  nor  sugar  alone  disintegrates  so 
rapidly.  Tablets  of  the  basic  bismuth  salts  made  with  the  addition 
of  20  per  cent,  of  cane  sugar  fairly  "  fly  to  pieces  "  when  dropped 
into  warm  water.    This  also  is  true  of  tablets  each  containing 
Bismuth  subnitrate  1  grain. 
Cerium  oxalate  %  " 
Milk  sugar  »  .  .  y2  1 ' 
Although  milk  sugar  is  distinctly  less  soluble  than  the  cane  sugar 
used  in  the  plain  bismuth  tablets.  Perhaps  the  most  striking 
example  of  rapid  disintegration,  where  least  expected,  is  in  a  tablet 
containing 
Reduced  iron  .  2  grains. 
Quinine  sulphate  1  grain. 
Arsenic  trioxide  -X  " 
when  granulated  with  syrup,  yet  none  of  the  ingredients  is  noted 
for  ready  solubility  in  water. 
The  cases  cited  and  numerous  others  lead  to  the  inference  that  a 
more  or  less  fixed  rule  applies  in  all  cases  where  a  tablet  is  com- 
posed of  two  or  more  ingredients;  namely,  that,  other  things  being 
equal,  the  rapidity  of  disintegration  of  a  tablet  varies  directly  with  the 
difference  in  solubility  of  the  ingredients.  The  reason  for  this  is 
obvious.    The  more  soluble  particles  being  first  attacked  by  the 
