i6o 
Pepsin  Adsorption  by  Charcoal. 
(Am. 
Jour.  Pharm. 
March,  1920. 
We  have  also  run  assays  for  total  cantharidin  (both  free  and  com- 
bined) by  modifying  both  the  Author's  Method  and  the  method  of 
Baudin,  by  the  addition  of  2  per  cent,  of  hydrochloric  acid  to  the 
first  solvent.  *  The  results  by  these  methods  are  still  higher,  but  the 
crystals  obtained  are  not  as  satisfactory  as  those  by  the  methods  for 
free  cantharidin  alone— the  resulting  crystals  not  being  as  pure  and 
free  from  resinous  matter. 
«  The  U.  S,  P.  makes  no  reference  to  the  presence  of  both  free  and 
combined  cantharidin  in  cantharides ;  but  the  assay  given  is  for  both 
the  free  and  combined,  hydrochloric  acid  being  added  to  liberate  the 
alkali-combined  cantharidin. 
We  have  never  seen  any  published  statement  as  to  whether  the 
combined  cantharidin  has  any  blistering  effect  when  applied  to  the 
skin,  but  have  assumed  heretofore  that  the  blistering  effect  is  due  to 
free  cantharidin  alone,  when  the  powdered  cantharides  is  used  as  an 
ingredient  of  a  blistering  plaster.  It  would  seem  that  this  also  is 
believed  to  be  true  in  the  case  of  the  official  tincture  where  no  at- 
tempt is  made  to  liberate  the  combined  cantharidin  before  making 
the  alcoholic  extraction.  On  the  other  hand,  acetic  acid  has  been 
incorporated  in  the  formulas  of  the  other  two  official  cantharides 
preparations,  Ceratum  Cantharidis  and  Collodium  Cantharidatum. 
Research  Laboratory, 
Johnson  &  Johnson, 
New  Brunswick,  New  Jersey. 
PEPSIN  ADSORPTION  BY  CHARCOAL. 
By  Norman  D.  Keeper,  P.D., 
pharmacist,     PENNvSYIvVANIA     state     SANITORIUM     FOR  TUBERCU1.0SIS, 
MONT  ALTO,  PA. 
Adsorption,  as  a  phenomenon,  has  been  practiced  for  centuries, 
b)ut  it  has  only  been  for  the  last  quarter  century  that  it  has  been  under- 
stood. Adsorption  is  a  condition  of  distribution,  wherein  the  sur- 
face rather  than  the  dispersed  phase  plays  the  important  r61e.  We 
k:now  that  bone  black  is  used  to  bleach  dark  sugar  juices,  extract 
fusel  oil  from  alcohol,  and  decolorize  dark  solutions  of  the  organic 
chemist.  And  now  we  are  to  learn  that  any  substance  which  causes 
a  marked  diminution  of  surface  tension  of  water,  such  as  fats,  soaps, 
albumin,  etc.,  are  very  readily  absorbed. 
