476  The  Ash  Content  of  Drugs.         j'^'^ctoZ'i' im*"' 
to  secure  a  representative  sample  of  a  root,  bark,  leaf  or  herb  that 
could  be  relied  upon  without  resorting  to  comminution  and  subse- 
quent mixing  of  an  appreciable  quantity  of  the  drug. 
This  difficulty  of  securing  representative  samples  of  many  crude 
drugs  has  no  doubt  deterred  the  revisers  of  some  of  the  more  recent 
pharmacopoeias  from  adopting  the  ash  content  factor  more  freely. 
It  is  generally  agreed  that  the  exact  method  for  determining  the 
residual  ash  should  be  described  so  as  to  obviate,  if  possible,  the 
likehhood  of  the  residue  retaining  an  undue  amount  of  unconsumed 
carbon. 
The  Ph.  Austr.  VIII,  despite  the  fact  that  it  includes  upwards 
of  150  limitations  for  the  ash  content  of  drugs,  does  not  provide  a 
method  for  determining  this  rather  important  requirement,  and  the 
several  critics  of  this  Pharmacopoeia  have  not  failed  to  assert  that 
the  commission  in  charge  of  the  revision  adopted  theoretic  rather 
than  practical  standards  for  many  of  the  pharmacopoeia!  drugs. 
The  Ph.  Helv.  IV  directs  that  ash  determinations  are  to  be  made 
by  heating  from  i  to  2  Gms.  of  the  substance  at  first  moderately, 
with  a  low  flame,  and  then  gradually  increasing  the  temperature 
until  the  residual  ash  is  free  from  carbon. 
The  nature  of  the  container  in  which  the  substance  is  to  be 
incinerated  is  not  specified  and  no  provisions  are  made  for  aiding 
the  combustion  of  protected  carbon  particles. 
The  new  German  Pharmacopoeia  process  is  much  more  complete. 
It  directs  that  a  suitable  quantity  of  the  substance  is  to  be  inciner- 
ated in  a  recently  heated  and  tared  crucible,  and  in  the  event  that 
complete  combustion  of  the  carbon  particles  is  not  brought  about 
by  continued  moderate  heating  the  material  is  to  be  leached  out 
with  hot  water  and  the  residual  carbon  again  heated  as  before. 
The  resulting  solution  is  subsequently  evaporated  and  the  weight 
of  the  dry  residue  is  added  to  that  of  the  ash. 
This  Ph.  Germ.  V  method  has  been  liberally  criticised,  many 
pharmacists  believing  that  the  leaching  out  method  is  much  more 
time-consuming  than  the  methods  which  involve  the  use  of  clean 
sand  for  distributing  the  particles  of  carbon  and  the  use  of  oxygen 
carriers  such  as  nitric  and  oxalic  acids  for  facilitating  combustion. 
Considerable  difference  of  opinion  appears  to  exist  regarding 
the  desirability  of  determining  the  ash,  and  other  analytical  factors, 
on  the  air-dried  drug  or  on  the  drug  dried  to  constant  weight  in  an 
exsiccator. 
