m2'  ^Solubility  of  Mercuric  Iodide  in  Fats.        {  ^™  De^iSs*'"'" 
equal  equivalents  of  biniodide  (eq.=227)  and  bichloride  (eq.=135*5) 
of  mercury,  only  traces  separating  in  course  of  time  of  the  slightly 
yellowish  white  crystalline  compound  already  mentioned. 
Iodide  of  potassium  increases  considerably  the  solubility  of  binio- 
dide of  mercury  in  castor  oil.  In  a  steam-bath,  at  a  temperature  near 
100°C.,  I  have  dissolved  easily  200  grams  of  the  compound  (HgI)2KI 
in  1,000  grams  of  castor  oil.  lodohydrargyrate  of  potassium,  which 
contains  73*1  per  cent,  of  its  weight  of  biniodide  of  mercury,  dis- 
solves, thererefore,  in  five  times  its  weight  of  castor  oil  at  a  tempera- 
ture near  100°.  The  solution  kept  for  three  weeks  at  a  temperature 
of  20°C.  gave  only  traces  of  a  yellow  crystalline  compound.  The 
solubility  of  the  iodiohydrargyrate  is,  therefore,  the  same  in  hot  and 
in  cold  castor  oil. 
Lard. — If  lard  be  melted  in  a  steani-bath  in  a  porcelain  dish,  and 
1*25  gram  of  biniodide  of  mercury  be  added  per  100  grams  of  lard, 
the  mixture  being  stirred  with  a  glass  pestle,  all  the  biniodide  can  be 
dissolved.  The  solution  is  clear  and  colorless ;  but,  upon  being  left  to 
cool,  it  becomes  rose-colored  in  solidifying  and  deposits  biniodide  of 
mercury,  which  can  be  seen  to  be  distinctly  crystalline  under  tlie 
microscope. 
WJien  this  solution — 12*5  grams  of  biniodide  in  1,000  grams  of 
lard — is  diluted  with  its  own  weight  of  lard  it  still  becomes  rose-col- 
ored in  solidifying,  and  deposits  crystals  of  biniodide  of  mercury. 
But  lard  which  contains  not  more  than  4*5  grams  of  biniodide  of  mer- 
cury in  1,000  grams  no  longer  deposits  crystals  of  the  biniodide  in 
cooling. 
Fase/m.  — Vaselin  dissolves  little  biniodide  of  mercury,  even  with 
the  aid  of  heat.  In  a  steam-bath,  and  using  a  small  glass  pestle  to 
rub  down  the  mercuric  compound,  the  quantity  dissolved  is  not  sensi- 
bly in  excess  of  2  grams  of  biniodide  in  1,000  grams  of  vaselin. 
The  solution  is  limpid  and  colorless.  Left  to  cool  it  becomes  strongly 
rose-colored ;  it  even  dej)osits  the  biniodide  upon  the  sides  of  the  cap- 
sule before  solidifying.  Upon  augmenting  gradually  the  quantity  of 
vaselin  the  solution  of  1  part  in  1,000  assumes  a  clear  salmon  tint  in 
cooling,  and  deposits  numerous  crystals  of  biniodide.  A  solution  of 
1  in  1,500  when  cool  has  a  very  marked  orange-rose  tint,  and  deposits 
very  distinct  crystals  of  biniodide.  From  a  solution  of  1  in  2,500 
there  still  separate  during  the  cooling  perfectly  distinct  crystals  in 
quantity  sufficient  to  impart  to  the  cold  mixture  a  slight  rose  color. 
