610  Solubility  of  Mercuric  Iodide  in  Feds.        {^""''DeT'  isS''™'  ' 
a  more  prolonged  trituration.  Upon  being  left  to  cool,  the  solution 
deposits  rather  rapidly  about  two-thirds  of  the  bmiodide  it  contained 
in  distinctly  formed  yellow  and  red  crystals. 
Almond  oil  heated  to  about  180°C.  dissolves  about  80  grams  of 
biniodide  of  mercury  in  1,000  grams.  Upon  this  solution  cooling  it 
deposits  numerous  sulphur-yellow  crystals  of  mercury  biniodide,  the 
deposit  being  pretty  considerable  by  the  time  the  temperature  has 
fallen  ,to  150°C.  Collected  upon  a  filter  these  crystals  pass  rapidly 
into  the  red  modification. 
Almond  oil  containing,  w^hile  hot,  8,  7,  or  6  grams  of  the  biniodide  in 
1,000  grams,  deposits  the  greater  part  of  its  excess  of  biniodide  before 
completely  cooling. 
I  have  preserved  without  deposit  and  for  several  days,  at  a  temper- 
ature of  25°C.,  almond  oil  containing  5  grams  of  biniodide  in  1,000 
grams ;  but  this  oil  deposited  a  notable  quantity  of  biniodide  when 
the  temperature  fell  to  about  18°C. 
Almond  oil  containing  not  more  than  4  grams  of  biniodide  of  mer- 
cury ])er  1,000  grams  has  remained  fifty  days  in  a  cold  cellar  without 
depositing  the  least  trace  of  biniodide.  It  may,  therefore,  be  consid- 
ered that  this  proportion — 4  in  1,000 — should  not  be  exceeded  in 
practice. 
In  these  experiments,  with  the  object  of  insuring  perfect  preserva- 
tion of  the  product,  I  used  almond  oil  that  had  been  previously  heated 
f()r  some  minutes  to  a  temperature  of  220°  to  250°C.,  and  filtered 
after  becoming  quite  cool.  This  treatment  of  the  oil  is  like  that  I 
adopted  in  obtaining  the  stable  phosphorated  oil  which  has  now  been 
included  in  the  French  Codex.  But  ahnond  oil  of  good  quality,  well 
filtered  and  not  previously  superheated,  gives  very  satisfactory  results. 
In  order  to  charge  almond  oil  with  a  larger  quantity  of  mercuric 
compound  recourse  may  be  had  to  various  other  compounds.  Potas- 
sium iodide,  for  example,  increases  the  solubility  of  biniodide  of  mer- 
cury in  almond  oil.  Upwards  of  50  grams  of  the  combination  (Hgl2)2, 
KI  can  be  dissolved  in  1,000  grams  of  the  oil.  For  instance,  2  grams 
of  biniodide  of  mercury  and  73  centigrams  of  iodide  of  potassium 
having  been  dissolved  in  a  steam-bath  in  50  grams  of  almond  oil,  the 
solution  after  remaining  six  weeks  in  a  cellar  had  only  deposited  some 
minute  crystals  of  biniodide,  due  probably  to  the  insufficient  purity  of 
the  commercial  iodide  of  potassium.  I  have  raised  the  quantity  of 
iadohydrargyrate  of  potassium  beyond  75  grams  per  kilogram  of  oil, 
