Am.  Jour.  Pharm.  | 
January,  1910.  j 
U.S. P.  Chemicals  and  Tests. 
29 
The  personal  equation  as  an  eminent  factor  goes  without  saying, 
and  all  lines  should  be  drawn  to  cut  this  factor  down  to  the  smallest 
possible  limitation  of  variations,  so  that  unnecessary  discussions  and 
correspondence  may  be  eliminated.  It  is  necessary  to  have  all  defini- 
tions and  tests  made  so  precise  that  there  can  be  no  question,  and  the 
best  and  uniform  methods  should  be  adopted  from  time  to  time  as 
occasion  may  arise,  so  that  there  may  be  concordant  results.  It  is 
well  understood,  of  course,  that  complete  laboratory  work  cannot 
always  be  accomplished  by  all,  but  finally  all  the  onus  really  comes 
on  the  manufacturer,  and  consequently  every  possible  precaution  is 
taken  to  protect  the  consumer.  The  productions  of  the  laboratory 
are  subjected  to  tests  by  chemists  who  have  nothing  to  do  with 
the  manufacturing  of  the  chemical,  and,  in  addition,  the  product  is 
not  allowed  to  leave  any  department  of  the  laboratory  until  the  actual 
manufacturer  is  satisfied  that  it  is  correct  in  every  particular.  A 
record  is  kept  of  every  lot,  and  its  history  may  be  traced  from  the 
time  of  its  production  until  the  time  when  the  label  bearing  its  par- 
ticular mark  is  destroyed. 
The  question  of  proper  apparatus  for  the  manufacture  of 
medicinal  chemicals  is  sometimes  very  perplexing.  There  are  at 
command  glass,  quartz,  porcelain,  earthenware,  enamelled,  metallic, 
and  vessels  of  every  description,  but  the  decision  as  to  which  is  best 
for  the  purpose  can  only  be  reached  by  long  experience,  and  even 
then  it  is  necessary  to  use  great  precaution,  so  that  the  resulting 
product  may  be  of  the  proper  purity,  and  it  is  often  necessary  that 
complex  apparatus  be  used  in  order  that  all  requirements  may  be 
met. 
That  all  manufacturers  desire  that  their  various  products  com- 
ing under  the  head  of  "  white  chemicals  "  should  be  of  the  whitest 
is  self-evident,  and  since  the  limit  of  iron,  whicn  is  practically  always 
present,  was  very  much  increased  in  the  heavy  metal  test,  it  is  pos- 
sible to  use  such  apparatus  which  otherwise  would  necessarily  have 
been  eliminated.  Iron  is  almost  always  the  cause  of  "  off-color," 
but  with  the  proper  care  its  effects  can  be  overcome,  and  even  the 
most  critical,  of  whom  there  are  multitudes,  can  be  satisfied.  A  more 
difficult  proposition  is  the  presence  of  mechanical  impurities, — atmos- 
pheric dust,  particles  of  carbon,  milling  dust,  fibres  from  filtering  and 
drying  materials,  small  pieces  of  wood  from  containers,  being  ever- 
lasting sources  of  annoyance,  and,  in  fact,  it  is  very  difficult  at  times 
to  convince  all  that  it  is  impracticable  to  manufacture  material  by 
