ON  PRECIPITATED  OXIDE  OP  MERCURY.  555 
passing  through  charcoal  impregnated  with  carbonate  of  potassa  or 
soda,  it  is  remarked  that  with  the  latter  it  is  necessary  to  heat  much 
more  powerfully  than  with  potassa  to  obtain  an  equal  quantity  of 
cyanide. 
But  with  animal  matters,  the  latter  are  too  quickly  decomposed  at 
a  very  high  temperature,  and  the  greater  part  of  their  nitrogen 
escapes  before  the  reduction  of  the  soda,  for  even  by  heating  very 
powerfully  (above  the  fusing  point  of  cast  iron),  the  production  is 
not  sensibly  increased  and  never  comes  near  to  that  of  potassa. — 
London  Chemist,  Sept.,  1858,  from  Comptes  Rendus)'No.  5,  Aug.  2, 
1858. 
ON  PRECIPITATED  OXIDE  OF  MERCURY. 
By  William  Wallace,  Ph.D.,  F.C.S.,  Glasgow. 
Mercuric  oxide,  prepared  by  treating  a  solution  of  corrosive 
sublimate  or  mercuric  nitrate  with  a  caustic  alkali,  was  formerly 
regarded  as  a  hydrate,  but  Millon,  Marchand  and  Pelouze  have 
declared  it  to  be  anhydrous.  Schaffner  states,  however,  that 
the  precipitated  oxide  contains  20  per  cent,  of  water,  and  de- 
duces from  his  analyses  the  formula  HgO,  3HO. 
Specimens  of  the  oxide  precipitated  and  dried  at  the  tempera- 
ture of  the  air,  and  at  212°,  were  carefully  prepared.  In  no 
case  did  the  precipitates  lose  more  than  about  1  per  cent,  on 
being  heated  to  incipient  decomposition.  The  oxide  appears  to 
be  decomposed  with  somewhat  greater  facility  on  the  first  appli- 
cation of  a  high  temperature,  than  after  having  been  strongly 
heated.  This  is  probably  owing  to  the  conversion  of  the  yellow 
oxide  into  the  red  by  the  action  of  heat. 
Solubility  in  water. 
1.  Recently  precipitated  mercuric  oxide  was  left  in  contact 
with  water  for  several  days,  the  mixture  having  been  repeatedly 
stirred  up.  200  cubic  centims.  of  the  fluid  gave  -001  of  oxide, 
or  1  part  in  200,000  of  water. 
2.  The  oxide  was  boiled  with  water  for  some  time,  and  the 
solution  allowed  to  cool.  250  cubic  centims.  of  the  filtered 
liquid  gave  -002  of  oxide,  or  1  part  in  125,000  of  water. — Lon- 
don Chem.  Q-azette,  Sept,,  1858. 
