80  Solubility  of  Compressed  Tablets.  {^ebr^vy,!^ 
sodium  bicarbonate  found.  Therefore,  for  all  commercial  purposes, 
a  Seidlitz-powder  analysis  consists  in  making  a  C02  determination, 
calculating  the  sodium  bicarbonate  therefrom,  and  (providing  the 
qualitative  test  shows  no  contaminating  impurities)  determining  the 
Rochelle  salt  by  difference. 
Before  concluding,  it  might  be  well  to  state  that  designs  for  carbon- 
dioxide  apparatus  are  to  be  found  in  nearly  all  reliable  text-books, 
and  many  of  them  can  be  simply  and  quickly  constructed. 
SOLUBILITY  OF  COMPRESSED  TABLETS. 
By  Anthony  M.  Hance. 
Among  *he  useful  forms  of  medicine  adopted'  in  recent  years 
there  is  none  of  greater  importance  and  value  than  compressed 
tablets.  Like  all  innovations  in  medicine,  their  adoption  was 
somewhat  slow.  The  physicians'  requirements  could  very  readily 
be  supplied  by  pills,  either  gelatin-  or  sugar-coated,  of  which  a 
large  variety  of  combinations  then  existed. 
The  tablet  form  of  medicine  possesses  important  advantages  not 
to  be  secured  otherwise,  such  as  minimum  of  bulk,  certain  and 
more  rapid  solubility  and  quicker  therapeutic  action.  Certain  com- 
binations which  readily  undergo  chemical  change  in  the  presence  of 
moisture  can  be  made  into  tablets  to  better  advantage  than  into 
pills.  Certain  conditions  may  be  successfully  treated  with  medicine 
in  tablet  form,  when  pills  would  be  impracticable,  as,  for  example, 
where  a  continuous  local  effect  is  desired. 
The  purpose  of  this  paper  is  to  call  special  attention  to  the  one 
all-important  and  absolutely  indispensable  quality  of  all  scientifi- 
cally compressed  tablets,  namely,  solubility.  Upon  this  one  quality 
alone  the  tablet,  as  a  form  of  medicine,  stands  or  falls. 
A  tablet  may  be  made  ever  so  accurately  and  conscientiously 
with  respect  to  purity  of  materials,  skill  in  manipulation,  a  fault- 
less check-system  to  guard  against  errors,  uniformity  in  weight  and 
size  and  handsome  appearance  ;  but,  if  the  one  quality  of  solubility 
is  wanting,  it  is  not  a  good  tablet. 
In  the  early  days  of  tablet  manufacture,  the  importance  of  solu- 
bility was  under-estimated.  The  distinct  advance  was  thought  to 
be  in  the  compression  of  the  drug,  thus  presenting  the  medicament 
independent  of  the  usual  substances  required  to  make  a  pill  mass. 
The  essential  quality  was  permanence  of  form. 
