OINTMENT  OF  MERCURIC  NITRATE. 
419 
curous  or  mercuric  salts  of  some  of  the  fattj  acids  either  origin- 
ally existing  in  the  fat  or  as  products  of  its  decomposition. 
This  is  amply  evidenced  by  employing  a  drying  oil,  as  the  oils  of 
cotton  or  flaxseed,  in  the  preparation  of  the  ointment,  which  of 
course,  as  will  be  seen,  are  entirely  inadmissible  for  this  pur- 
pose. If  flaxseed  oil,  for  instance,  is  heated  with,  nitric  acid 
alone,  even  until  the  latter  is  entirely  consumed,  no  separation 
will  take  place  ;  but  if  to  the  heated  oil  the  mercurial  solution  be 
added,  a  greenish-yellow  agglutinated  mass  immediately  sepa- 
rates, which  adheres  to  the  bottom  of  the  vessel  and  the  stirrer 
too  tenaciously  to  admit  of  distribution,  and  moreover  hardens 
on  cooling  to  the  consistence  of  lead  plaster.  Strong  cold  nitric 
acid  has  no  apparent  action  on  this  substance ;  neither  have  oil 
of  turpentine,  alcohol,  ether  and  carbon  disulphide,  when  repeat- 
edly treated  with  these  solvents  in  succession ;  but  chloroform 
dissolves  the  greater  part  of  it,  leaving  a  grayish,  light,  floccu- 
lent  deposit,  which  agglutinates  on  the  addition  of  alcohol.  Cold 
strong  nitric  acid  attacks  this  powerfully,  forming  a  green  solu- 
tion containing  abundance  of  mercuric  oxide.  At  the  same  time- 
a  yellow,  oily  substance  separates,  which  completely  dissolves- 
in  chloroform — also  in  ether,  but  slowly  and  imperfectly  in  air 
cohol — to  an  intense  yellow  color,  and  saponifies  with  potassium 
hydrate  to  a  deep  red  col(fi\  The  original  resinous  substance^ 
as  it  separates  from  the  supernatant  oily  liquid,  is  but  faiatly 
acted  on  by  cold  strong  nitric  acid  ;  but  the  same  acid  when  hot 
dissolves  all  but  a  yellow  oil  which  separates  from  the  solution.;^, 
and  contains  mercury  in  abundance,  as  the  black  precipitate 
with  ammonium  sulphide  indicates.  The  first  chloroformic  so- 
lution of  the  resinous  deposit  when  evaporated  leaves  a  reddish- 
yellow,  varnish-like  residue,  which  is  insoluble  in^water,  but 
readily  saponifies  with  potassium  hydrate  to  a  red  solution,  whilst 
a  small  quantity  of  mercurous  oxide  at  the  same  time  separates. 
By  the  addition  of  nitric  acid  to  a  solution  of  this  soap,  a  yellow 
precipitate  again  occurs. 
The  separation  of  this  resinous  deposit  at  the  very  outset  of 
the  operation  goes  to  sliow  how  easily  the  mercurial  nitrates  are 
reduced  by  heat,  or,  more  particularly,  by  the  combined  influ- 
ence of  temperature  and  the  reducing  property  of  the  organic 
