338 
ON  HYDRARGYRI  IODIDUM  VIRIDE,  B.  P. 
the  point  at  which  I  was  to  transfer  the  product  to  filter  in  g- 
jjaper  and  dry  it  by  exposure  in  a  dark  room.  But  instead  of 
doing  this  I  continued  the  trituration  until  the  mass  was  dry. 
As  the  rubbing  proceeded  I  found  the  green  color  rapidly  disap- 
peared, the  powder  became  more  and  more  yellow,  and  the  ulti- 
mate result  was  a  yellow  substance  with  a  dingy  greenish  tint 
upon  it.  The  question  that  arose,  therefore,  was  to  ascertain 
the  composition  of  the  product  at  the  two  periods  ;  namely,  at 
the  period  in  which  it  was  decidedly  green,  and  at  the  subse- 
quent period  when  it  became  permanently  yellow.  To  solve  this 
point  200  grains  of  mercury  and  127  grains  of  iodine  were  tri- 
turated with  a  little  spirit  until  the  dark  green  color  was  ob- 
tained. [A  portion  of  this  iodide  was  then  taken  for  immediate 
analysis,  and  the  remainder  put  [in  a  dark  place  to  dry.  The 
analysis  was  effected  as  follows  : — 
A  known  quantity  of  the  iodide  was  washed  with  boiling  abso- 
lute alcohol,  the  washings  evaporated  to  dryness,  and  the  resi- 
due weighed  ;  it  consisted  of  red  or  mercuric  iodide.  The  insolu- 
ble portion  was  dried  and  divided  into  two  parts;  one  was  dissolved 
in  hydrochloric  acid  and  chlorate  of  potash,  the  solution  evapo- 
rated to  near  dryness,  diluted,  precipitated  with  stannous  chlo- 
ride, and  the  precipitated  metallic  mercury  collected  and  weighed; 
the  other  half  of  the  powder  was  digested  with  finely  granulated 
zinc  and  diluted  acetic  acid,  whereby  an  amalgam  of  zinc  was 
formed,  the  iodine  passing  into  solution  as  hydriodic  acid.  After 
some  time  the  liquid  was  poured  off,  nitrate  of  silver  added  to 
it,  and  the  precipitated  iodide  of  silver  collected  and  weighed. 
Other  methods  of  analysis  were  also  employed,  but  the  above 
were  found  sufficiently  satisfactory.  As  some  objections  might 
be  taken  to  the  use  of  boiling  alcohol,  the  red  iodide  was  also 
estimated  by  washing  with  ether. 
The  result  of  the  analysis  of  the  green  powder  was  as  follows, 
the  moisture  being  excluded  : — 
Mercuric  Iodide,  Hgl2  .  .  .  28-6 
Mercurous  Iodide,  Hgl  .  .  .  58*4 
Metallic  Mercury,  Hg       .       .       .  13*0 
100-0 
