THE  AMEEIOAN 
JOURNAL  OF  PHARMACY 
JULY,  igii 
VOLUMETRIC  DETERMINATION  OF  MERCURY. 
By  Carl  E.  Smith. 
Laboratory  of  the   Powers-Weightman-Rosengarten   Co.,  Philadelphia. 
Abstracts  oi  a  Report  by  a  Committee  of  the  Division  of  Pharma- 
ceutical Chemistry  of  the  American  Chemical  Society  have  appeared 
in  recent  journals  (see  this  Journal,  191  i,  v.  83,  p.  186),  the  work 
reported  on  being  a  comparison  of  various  methods  for  the  deter- 
mination of  mercury  in  the  medicinal  compounds  of  this  metal. 
The  purpose  of  these  notes  is  to  relate  some  recent  experiences 
with  two  of  these  methods,  which  are  probably  the  simplest  and  most 
reliable  of  those  mentioned  in  the  report,  the  Hempel  method  for 
mercurous  and  the  Rupp  method  for  mercuric  compounds.  It  is 
desired  also  to  call  attention  tO'  one  other,  which  is  perhaps  the  best 
volumetric  method  available  for  some  purposes. 
The  writer's  experience  with  the  Hempel  method,  in  its  appli- 
cation to  calomel  and  mercurous  iodide,  corroborates  to  a  consider- 
able extent  the  results  of  the  committee.  The  objectionable  feature 
of  it,  noted  by  several  of  the  members,  that  long-continued  shaking 
is  needed  to  bring  the  salt  into  solution,  may  be  eliminated,  it  was 
found,  by  the  simple  change  of  adding  the  iodine  solution  first,  in- 
stead of  the  potassium  iodide.  When  this  is  done  and  the  mixture 
at  once  shaken  vigorously  in  a  stoppered  flask,  solution  is  effected 
very  quickly.  The  final  result  is  the  same  in  either  case,  as  com- 
parative trials  have  shown.  It  seems  advisable,  also,  to  increase 
the  quantity  of  sam])le,  to  lessen  the  experimental  error,  in  the  case 
of  calomel  to  about  i  Cim.  The  most  satisfactory  results  were 
obtained  when  working  in  the  following  manner:  To  about  i  Gm.  of 
calomel,  accurately  weighed,  contained  in  a  glass-stoppered  300  c.c. 
(311) 
