PROCESS  FOR  QUANTITATIVE  ESTIMATION  OF  MERCURY.  457 
liquid  and  be  removed  in  any  suitable  manner,  while  the  heavier 
substance  unites  at  the  bottom  of  the  vessel. 
This  is  the  mode  of  proceeding.  A  given  quantity  of  the 
mercurial  ointment  to  be  examined,  say  five  grammes,  is  to  be 
weighed,  and  introduced  into  a  small  flask  with  a  flat  bottom. 
Bisulphide  of  carbon,  in  sufficient  quantities  to  dissolve  the  fat, 
is  added,  and  the  mixture  agitated  for  some  minutes  to  promote 
the  solution  of  the  fatty  matter.  There  is  now  to  be  added  a 
solution  of  chloride  of  calcium  of  specific  gravity  1.38.  The 
mixture  is  agitated  and  then  allowed  to  stand.  In  about  eight 
or  ten  minutes  the  separation  of  the  ingredients  will  be  com- 
plete. The  bisulphide  of  carbon  holding  the  fat  in  solution  will 
form  the  upper  stratum,  beneath  which  will  be  the  saline  solu- 
tion, and  below  this  the  mercury  in  a  finely  divided  state.  Any 
foreign  matter  that  may  have  been  present,  will  be  either  mixed 
with  the  mercury  or  diffused  through  one  of  the  upper  strata. 
The  solution  of  fat  in  sulphide  of  carbon  is  to  be  decanted|  off, 
and  a  fresh  portion  of  sulphide  of  carbon  added  to  remove  any 
remaining  portions  of  fat  that  may  be  adhering  to  the  sides  of 
the  vessel,  or  to  the  other  ingredients,  and  this  is  again  to  be 
decanted  off. 
The  mercury  will  be  found  at  the  bottom  of  the  vessel,  mixed 
mechanically  with  any  foreign  matters  that  may  have  been 
present.  For  estimating  the  quantity  of  the  mercury,  I  employ 
the  method  proposed  by  M.  Barreswil  for  the  analysis  of  mer- 
curial minerals,  and  which  consists  in  melting  a  fragment  of  fu- 
sible metal  in  water,  at  the  bottom  of  which  is  the  mercury  to 
be  estimated.  The  following  is  the  mode  of  proceeding  in  this 
part  of  the  process  : — After  the  fat  has  been  removed  by  means 
of  sulphide  of  carbon,  there  will  remain  in  the  flask  the  saline 
solution  and  the  mercury,  with  any  foreign  matter.  To  this 
is  added  a  weighed  quantity  of  fusible  metal,  and  heat  is  applied. 
When  the  metal  is  fused,  it  is  slightly  agitated  until  all  the  mer- 
cury has  been  taken  up  by  the  fused  mass,  and  the  vessel  is  then 
allowed  to  cool,  or  the  cooling  is  promoted  by  the  application  of 
cold  water.  When  this  has  taken  place  the  metallic  button  is 
taken  out,  washed  dried  and  weighed.  The  augmentation  of 
weight  which  the  fusible  metal  is  found  to  have  acquired,  will, 
of  course,  represent  the  quantity  of  mercury. 
