^'•^^'^^^'^Pharmacopoeial  Assays  of  Drugs  and  Galenicals.  223 
mony  obtained  by  the  spontaneous  evaporation  of  the  latex  of  the 
living  scammony  root. 
In  the  two  cases  cited  the  requirements  are  clear  and  unmistak- 
able, as  a  legal  requirement  should  be,  and  it  will  be  observed  that 
such  is  also  the  case  with  the  few  other  drugs  for  which  processes  of 
assay  have  been  introduced  into  the  last  Pharmacopoeia. 
The  officinal  process  for  determining  the  digestive  strength  of 
pepsin  may  not  be  the  best  that  can  be  devised ;  but  in  connection 
with  the  described  physical  characteristics  identifies  the  article  with 
sufficient  exactness  and  establishes  a  minimum  standard  of  quality 
which  is  perfectly  reliable  for  the  conditions  given. 
On  assaying  cinchona  bark  for  total  alkaloids  by  the  pharma- 
copceial  process,  the  resulting  product  consists  of  quinine,  cinchonine 
and  allied  alkaloids,  provided  the  identity  of  the  bark  as  being 
derived  from  a  species  of  Cinchona  or  of  Remijia  has  been  estab- 
lished ;  for  by  the  same  process  a  number  of  poisonous  alkaloids 
may  be  prepared  ;  and  if,  for  instance,  a  strychnos  bark  (some  of 
which  are  now  met  with  in  commerce)  were  tested  in  the  same  manner, 
strychnine  and  brucine  would  finally  be  weighed.  It  follows  from 
this  that,  if  cinchona  bark  or  its  powder  had  become  accidentally 
mixed  with  strychnos  bark,  the  alkaloids  of  the  latter  would  be 
weighed  as  cinchona  alkaloids.  The  same  is  also  true  of  berberine, 
hydrastine,  and  some  other  non-poisonous  alkaloids  which  are  not 
freely  soluble  in  a  solution  of  sodium  hydrate.  The  pharmacopceial 
estimation  of  quinine,  which  is  based  upon  the  sparing  solubility  of 
its  sulphate  in  water,  excludes  all  other  alkaloids  likely  to  be  met 
with,  even  berberine  sulphate  being  more  freely  soluble  in  neutral 
aqueous  liquids ;  but  if  crystallizing,  would  reveal  its  presence  by  its 
yellow  color.  It  will  thus  be  seen  that,  while  the  pharmacopceial 
requirements  for  the  percentage  of  quinine  are,  according  to  our 
present  knowledge,  sufficiently  perfect  as  a  legal  standard,  the  assay 
for  total  alkaloids  can  be  thus  regarded  only  in  connection  with  the 
absolute  identity  of  the  drug  itself. 
The  remaining  drug  for  which  the  present  pharmacopoeia  pre- 
scribes a  process  of  assay  is  jalapa,  which  is  required  to  contain  at 
least  12  per  cent,  of  resin  of  which  not  over  10  per  cent.  (1-2  per 
cent,  of  the  drug)  should  be  soluble  in  ether.  These  requirements 
should  be  considered  in  connection  with  those  given  under  resina 
jalapce,  excepting  the  faulty  one  with  ammonia  water,  and  are  suffi- 
