164 
ME.  G.  B.  BUCKTOIS'  ON  THE  ISOLATION 
to  drive  off  the  iodide  of  methyl,  and  the  crystalline  mass,  after  separation  firom  the 
excess  of  mercury  by  pressure  in  a cloth,  vras  powdered  and  exposed  to  the  air  for  some 
hours  to  remove  every  trace  of  iodide  of  methyl. 
This  crude  mass  was  generally  employed  in  the  following  experiments,  but  the  pure 
compound  may  be  expeditiously  obtained  by  dissolving  the  crystals  in  hot  aqueous  potash. 
By  the  addition  of  weak  hydrochloric  acid,  which  must  not  be  in  excess,  the  substance 
is  again  precipitated.  A subsequent  washing  in  water,  in  which  it  is  almost  insoluble, 
yields  it  pure  and  colourless. 
Aqueous  cyanide  of  potassium  acts  very  slowly  upon  iodide  of  hydrargyromethylium, 
and  requires  a temperature  approaching  to  200°  C.  before  mercury  is  reduced. 
The  volatile  matters  formed,  exert  a pressure  that  few  glass  tubes  can  resist,  even 
when  assisted  by  an  atmosphere  of  steam.  Much  better  results  were  obtained  by  the 
following  method. 
Dry  iodide  of  hydrargyromethylium  was  rubbed  in  a mortar  with  finely  divided  cyanide 
of  potassium,  and  distilled  in  flasks  over  the  naked  gas  flame. 
Small  charges  and  frequent  operations  are  better  than  acting  on  large  portions.  A 
gas  passes  with  an  odour  something  like  that  of  trimethylamine ; also  water,  ammonia, 
and  finally,  a heavy  liquid  which  is  not  miscible  with  water.  The  residue  in  the  flask 
contains  iodide  and  carbonate  of  potassium,  paracyanogen,  and  metallic  mercury.  A 
portion  of  iodide  of  hydrargyromethylium  always  sublimes. 
The  distillate  was  agitated  with  water,  and  the  lower  stratum;  which  was  comparatively 
small  in  amount,  was  twice  rectified  over  chloride  of  calcium  at  the  temperature  of  the 
water-bath. 
This  liquid  has  the  following  properties : — -It  is  colourless,  highly  refractive  to  light, 
and  almost  wholly  insoluble  in  water.  When  pure,  it  has  a faint  and  somewhat  sweetish 
odour,  but  the  crude  product  is  contaminated  with  the  offensive  body  that  always  accom- 
panies the  decomposition  of  methyl  compounds  when  heated  with  cyanide  of  potassium. 
The  odour  may  be  entirely  removed  by  agitation  with  very  dilute  sulphuric  acid. 
This  liquid  is  very  combustible,  and  burns  with  a luminous  flame  and  abimdant 
evolution  of  mercurial  vapour.  It  is  soluble  in  all  proportions  in  alcohol  and  in  ether, 
from  the  former  of  which  it  is  precipitated  on  addition  of  water.  The  vapour  detonates 
loudly  when  exploded  with  oxygen  gas. 
This  preparation  began  to  boil  at  93°,  at  which  point  it  remained  constant  until  about 
fths  of  the  whole  had  passed  over ; the  remainder  came  over  between  93°  and  96°  C. 
The  specific  gravity  of  the  former  portion  was  found  to  be  3*069,  from  which  it  appears 
to  be  the  heaviest  of  known  non-metallic  liquids.  A solid  glass  rod  floats  freely  on  its 
surface 
The  pure  substance  contains  neither  iodine  nor  cyanogen ; still  it  is  very  difficult  to 
separate  every  trace  of  iodide  of  hydrargyromethylium  which  volatilizes  mth  the  vapour. 
* The  specific  gravity  of  bromine  at  15°  is  2*98.  Selenic  acid,  with  one  equivalent  of  water,  Mitschee- 
i/iCH  found  to  have  a density  of  2*85. 
