^FetauaryTisM™'}     Solubility  of  Compressed  Tablets.  81 
It  seemed  sufficient  to  compress  the  drug  with  such  firmness  that 
the  finished  product  would  not  crumble  from  age  nor  break  from 
attrition  in  handling  or  transportation.  This  was  a  mistaken  idea. 
Such  tablets  were  improperly  made,  and  no  more  certain  to  produce 
the  desired  therapeutic  effects  than  improperly  made  mass  pills. 
The  distinct  advance  of  compressed  tablets  over  other  forms  of 
medicine  lies  in  the  fact  that  they  present  the  drug  in  permanent 
and  accurate  subdivision  and  soluble  form,  and  the  up-to-date  tab- 
let is  nothing  if  it  does  not  possess  the  quality  of  ready  solubility. 
Firmness,  or  that  degree  of  hardness  which  gives  form  and  per- 
manency to  tablets,  is  essential  in  all  well-made  tablets,  but  neither 
prevents  nor  assures  solubility, 
A  tablet  which  may  be  readily  crushed  with  the  fingers  may  or 
may  not  possess  the  proper  degree  of  solubility,  while  it  is  gener- 
ally not  firm  enough  to  be  especially  serviceable. 
The  term  solubility  as  applied  to  tablets  indicates  power  to  disin- 
tegrate rather  than  power  to  form  solutions.  It  refers  to  the  tablet 
mass  solely,  the  medicament  of  which  is  frequently  one  or  more 
insoluble  drugs,  as,  for  example,  calomel,  charcoal,  etc. 
A  tablet  is  soluble  when,  in  the  presence  of  the  proper  medium, 
it  promptly  disintegrates,  thus  liberating  in  a  minutely  subdivided 
condition  the  medicament  it  bears. 
The  degree  of  solubility  is  easily  influenced  by  the  nature  of  the 
component  part.  Thus  solid  extracts,  resinous  substances  and  cer- 
tain drugs,  such  as  reduced  iron  or  corrosive  sublimate,  make  tablets 
which  disintegrate  more  slowly  than  others  containing  dissimilar 
substances.  Tablets  of  corrosive  sublimate  are  rendered  more  freely 
soluble  than  they  would  otherwise  be  by  the  addition  of  substances 
which  favor  solution,  as,  for  example,  muriate  of  ammonia. 
In  certain  tablets  solubility  is  relative,  and  quite  unavoidably  so. 
In  others  it  is  intentionally  of  slow  degree.  Throat  tablets,  in 
which  by  slow  disintegration  a  continued  local  effect  is  sought,  are 
familiar  examples  of  the  latter.  In  tablets  for  making  extempo- 
raneous solutions,  and  in  hypodermic  tablets  especially,  rapid  disin- 
tegration and  solution  are  desirable. 
The  determination  of  this  solubility  is  a  matter  of  considerable 
importance.  The  process  is,  apparently,  quite  simple.  Drop  a 
properly  made  tablet  into  a  quantity  of  water  and  note  the  result. 
Immediately  the  form  of  the  tablet  changes  and  disintegration 
rapidly  follows. 
