58  ON  THE  REVISION  OF  THE  U.  S.  PHARMACOPOEIA. 
and  more  lively  in  color  the  better,  provided  it  be  thoroughly 
dry.  That  which  has  a  dead  color,  approaching  to  a  dull  olive, 
always  contains  largely  of  metallic  mercury,  and  iodides  that 
have  been  subjected  to  the  action  of  light  and  moisture. 
The  preparation  should  never  be  dispensed  without  the  most 
careful  testing,  and  it  is  fortunate  that  this  testing  is  very  sim- 
ply and  easily  performed.  A  small  quantity  of  iodide  of  mer- 
cury rubbed  in  a  mortar  with  a  little  strong  alcohol,  if  it  con- 
tains any  red  iodide,  will  invariably  exhibit  a  red  coloration  in 
the  track  of  the  pestle  as  the  alcohol  evaporates  from  the  sur- 
face of  the  mortar.  Or,  if  a  portion  to  be  examined  be  shaken 
in  a  test  tube  with  alcohol,  and  the  alcohol  evaporated  from  a 
porcelain  or  glass  surface,  the  most  minute  proportion  of  red 
iodide  becomes  visible.  If  it  be  desired  to  estimate  the  quan- 
tity,— or  rather  to  establish  the  presence  of  metallic  mercury, — 
the  iodide  should  be  rubbed  with  a  moderate  degree  of  pressure 
upon  any  surface  of  gold. 
In  concluding  the  unsatisfactory  notice  of  this  preparation, 
the  writer  submits  the  opinion  that,  unless  some  discriminating 
solvent  can  be  found  for  the  separation  of  these  lower  iodides  of 
mercury,  it  is  adapted  to  medical  use. 
Hydrargyri  Iodidum  Rubrum. 
Some  years  ago  Dublanc  proposed  to  prepare  this  iodide  by 
a  process  of  direct  combination  through  the  intervention  of  al- 
cohol, and  the  writer  has  found  a  slight  modification  of  M.  Du- 
blanc's  process  much  more  easy,  convenient,  and  economical 
than  the  officinal  one,  while  it  is  only  liable  to  the  objection  that 
it  necessarily  contains  the  insoluble  impurities  of  the  materials  ; 
an  objection  of  but  little  practical  weight,  since  it  has  never 
been  urged  in  the  case  of  the  green  iodide,  though  that  is  given 
in  much  larger  doses. 
Take  of  Mercury,  one  ounce. 
Iodine,  ten  drachms. 
Alcohol,  four  fluid-ounces. 
Introduce  the  mercury,  iodine,  and  half  the  alcohol  into  a 
four-ounce  vial,  and  shake  the  mixture  occasionally  during  two 
days,  or  until  the  combination  is  effected.  Should  the  alcohol 
become  colorless  during  the  process,  iodine  in  minute  portions 
