268  MERCURY — ITS  OXIDES  AND  ACETATES,  ETC. 
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chlorides  so  completely,  that  the  solution  is  not  afterwards  af- 
fected by  alkaline  sulphides. 
Separation  of  the  Oxides  in  acetic  solution. — The  oxides  are 
readily  recognized  by  appropriate  regeants  when  in  separate  so- 
lution, but  when  the  two  are  mixed,  and  the  solution  dilute,  the 
separation  and  recognition  of  the  acetate  of  the  red  oxide  is  not 
so  readily  effected. 
The  acid  solution  is  the  only  reliable  one  which  offers  ;  for  the 
mercurous  salt  if  evaporated  to  obtain  a  solution  free  from  ex- 
cess of  acid,  is  liable  to  conversion  into  the  mercuric  salt. 
The  mother  water  from  which  crystals  of  the  neutral  acetate 
of  mercurous  oxide  were  obtained,  was  found  to  contain  acetate 
of  mercuric  oxide. 
Caustic  potash  affords  a  yellow  precipitate,  with  slightly  acid 
solution  of  mercuric  oxide,  containing  1  part  in  900  of  water. 
The  presence  of  a  small  amount  of  chloride  of  sodium  or  ammo- 
nium does  not  prevent  the  reaction,  while  the  mercurous  salt  is 
precipitated  by  the  chlorides,  so  that  potash  does  not  disturb  the 
filtered  solution. 
When  acid  solutions  made  in  the  cold,  of  the  acetates,  con- 
taining a  grain  each  to  the  ounce,  are  mixed,  and  a  quarter  of 
an  ounce  of  the  mixed  solutions,  equal  to  a  quarter  of  a  grain  of 
each  oxide,  precipitated  by  chloride  of  sodium,  the  liquid  close- 
ly filtered  and  evaporated  to  near  dryness,  at  a  temperature  not 
exceeding  200°F.,  re-dissolved  in  a  small  portion  of  water  di- 
vided into  two  portions  and  treated,  one  with  caustic  potash,  and 
the  other  with  caustic  ammonia,  satisfactory  evidence  of  the  pre- 
sence of  red  oxide  is  adduced  ;  without  the  evaporation  following 
the  precipitation  of  the  numerous  salts,  the  result  is  very  unsat- 
isfactory. 
The  process  which  answered  best  to  detect  the  Oxides  of  Mer- 
eury  in  Blue  Mass,  was  to  wash  the  mass  in  the  dark,  with  small 
portions  of  cold  distilled  water,  in  a  small  flask,  by  agitation 
and  decantation,  till  all  coloring  matter  and  sugar  was  removed  ; 
then  digest  cold,  with  one  part  glacial  acetic  acid,  and  four  parts 
of  water  ;  filter,  and  if  any  mercury  is  present,  as  will  be  shown 
by  trying  a  small  portion  of  the  filtrate  with  sulphide  of  ammo- 
nium, evaporate  the  acetic  solution  at  a  low  heat,  nearly  to  dry- 
ness ;  re-dissolve  in  a  small  portion  of  water ;  precipitate  the 
