140 
Kernels  Quinine  Test 
Am.  Jour.  Pharm. 
March,  1887. 
If  it  be  attempted  to  appraise  that  tolerance  by  expressing  the  quan- 
tity of  foreign  bases  that  may  be  present  in  quinine  sulphate  which  is 
shown  by  the  test  to  be  acceptable,  the  result  will  be  a  failure.  Hith- 
erto I  have  supposed,  for  greater  simplicity  of  exposition,  that  the 
impurity  is  exclusively  cinchonidine  sulphate.  This  is  at  the  present 
time  most  frequently  the  case,  but,  sometimes,  other  bases  also  occur 
in  the  commercial  product,  though  less  frequently.  Those  bases,  be- 
ing unequally  soluble  in  ammonia,  the  delicacy  of  the  test  in  reference 
to  each  of  them  will  be  inversely  as  their  solubility,  and  the  tolerance 
will  be  variable. 
Nor  is  this  all,  for  in  considering  only  the  admixture  of  cinchoni- 
dine, and  admitting  a  fixed  temperature,  say  60°  C.  for  instance,  as 
being  adopted  in  practice,  that  is  to  say,  by  reducing  the  problem  to 
the  most  simple  form,  it  is  still  impossible  to  arrive  at  a  perfectly  sat- 
isfactory conclusion.  When  1  gram  of  quinine  sulphate  is  treated 
with  10  cc.  of  water,  the  solution  is  only  partial  even  at  100°  C, 
and  the  interior  parts  of  the  crystals  escape  the  action  of  the  solvent 
entirely. 
Under  these  conditions  it  will  happen  that  for  a  given  amount  of 
cinchonidine  in  a  sample  of  salt  tested,  if  the  impurity  arises  solely 
from  imperfect  drainage  off  of  the  mother-liquors  and  is  superficial, 
the  proportion  of  cinchonidine  that  will  pass  into  the  solution  will  be 
greater  than  if  the  impurity  be  due  to  cinchonidine  actually  in  the 
crystals.  Consequently  the  delicacy  of  the  test  would  be  greater  in 
the  former  case  than  in  the  latter  and  the  tolerance  would  be  less  in 
that  case.  Moreover,  when  it  is  noted  that  the  crystals  vary  in  size 
and  present  a  varying  surface,  that  they  are  not  generally  homogen- 
eous, that  the  distribution  of  the  cinchonidine  through  the  interior  of 
them  necessarily  alters  according  to  the  circumstances  of  the  crystalli- 
zation, etc.,  it  is  impossible  to  avoid  recognizing  that  the  tolerance  to 
be  appraised  will  have  a  considerable  range  of  variation.  Therefore, 
I  cannot  express  by  figures  having  any  precision  the  increase  of  the 
tolerance  corresponding  with  the  application  of  the  test  at  tempera- 
tures between  15°  and  100°  C.  With  cinchonidine  sulphate  as  the 
sole  impurity,  and  taking  60°  C.  as  the  temperature  for  making  the 
solution,  the  quantity  of  foreign  substance  passing  unnoti  ed  appears 
to  vary  between  4  and  5  per  cent.  The  magnitude  of  this  amount 
may  perhaps  be  an  argument  in  favor  of  raising  the  temperature  to  be 
adopted  ;  but  this  is  a  point  which  I  merely  mention  here  as  deserv- 
