424  Commercial  ^inia  Sulphate.  \^'^' 
not  always  been  of  such  a  nature  as  to  decide  the  question  satisfacto- 
rily or  at  all,  and  it  is  somewhat  notorious  that  sulphate  of  quinia  has 
very  frequently  contained  such  an  amount  of  cinchonidia  sulphate  as 
to  be  very  far  from  entitled  to  ranic  as  a  pure  preparation.  That  this 
should  be  the  case  is  to  a  great  extent  intelligible  from,  the  circum- 
stance that  of  late  years  it  is  said  there  has  been  in  the  manufacture  of 
quinia  a  much  larger  use  of  those  varieties  of  cinchona  bark  that  con- 
tain considerable  amounts  of  cinchonidia. 
Three  years  ago  attention  was  directed  to  this  subject  at  an  evening 
meeting  of  the  Pharmaceutical  Society,  and  it  was  shown  that  several 
commercial  samples  of  quinia  sulphate  contained  from  5  to  10  per  cent, 
of  cinchonidia  sulphate.  It  was  also  shown  that  the  indications  fur- 
nished by  the  test  directed  in  the  British  Pharmacopoeia  were  not  such 
as  to  give  evidence  of  this  impurity,  and  that  there  was  really  no  dif- 
ference between  the  result  obtained  in  testing  such  samples  and  that 
obtained  in  testing  really  pure  quinia  sulphate.  At  that  time  it  was 
suggested  that  a  test  based  partly  upon  the  different  solubilities  of  the 
sulphates  of  quinia  and  cinchonidia  in  water,  and  partly  upon  the  differ- 
ent solubilites  of  the  corresponding  alkaloids  in  ether,  would  be  more 
useful  for  ascertaining  the  purity  of  quinia  sulphate  than  either  the  test 
of  the  British  Pharmacopoeia  or  even  that  introduced  years  before  by 
Dr.  Kerner.  Somewhat  later  almost  exactly  the  same  mode  of  testing 
quinia  sulphate  was  recommended  by  Dr.  Hesse,  who  described  a  form 
of  apparatus  in  which  the  operation  was  to  be  conducted,  and  laid  down 
rules  by  which  some  approximative  estimate  might  be  formed  as  to  the 
amount  of  impurity  present  in  the  quinia  sulphate  operated  upon. 
It  is  in  regard  to  this  point  that  there  is  the  greatest  difficulty  in 
obtaining  trustworthy  results  by  any  of  the  known  methods  of  testing 
quinia  sulphate.  Even  with  Kerner's  test  applied  volumetrically  the 
results  obtained  are  liable  to  vary  under  the  influence  of  slight  differ- 
ences of  the  conditions  of  experiment,  and  at  the  time  when  that  test 
was  introduced  the  knowledge  of  the  alkaloids  associated  with  quinia 
was  sufficiently  imperfect  to  give  rise  to  additional  uncertainty  ;  now, 
however,  it  may  be  taken  as  certain  that  in  almost  every  case  the 
impurity  met  with  in  commercial  quinia  sulphate  is  nothing  more  nor 
less  than  cinchonidia  sulphate.  The  great  solubility  of  cinchonia 
sulphate  as  compared  with  quinia  sulphate  is  alone  almost  a  guarantee 
that  it  cannot  be  present  in  a  well  prepared  sample  of  quinia  sulphate. 
As  regards  quinidia,  again,  the  probability  of  its  occurrence  is  very 
