546  Germanium  and  its  Compounds.  {AmN?vf'i§6arm* 
agent ;  it  converts  chromic  acid  into  chromium  oxide,  hypermanganic 
acid  into  manganous  oxide,  and  precipitates  gold  solutions  brown ; 
from  bichloride  of  mercury  solutions  it  throws  down  first  calomel 
then  mercury,  and  bleaches  litmus  instantly. 
Germanium  dioxide  (Germanic  acid  ? ),  Ge02,  is  formed  by  burning 
the  element  in  oxygen,  or  by  oxidation  with  nitric  acid,  or  by  roast- 
ing the  sulphide.  The  pure  oxide  can  be  obtained  by  decomposing 
germanic  chloride  (GeCl4)  with  water,  but  the  yield  is  trifling. 
Germanic  oxide  is  a  dense  white  powder  of  specific  gravity  4*703. 
One  part  of  the  oxide  requires  for  solution  at  20°  C.  247-l  parts,  at 
100°  C,  95'3  parts  of  water.  The  solution,  when  evaporated,  yields 
small  microscopic  crystals.  Carbon  or  hydrogen  reduces  it  to  ger- 
manium. Germanic  oxide  is  sparingly  soluble  in  acids,  and  possesses 
the  characteristics  of  an  acid,  which  accounts  for  the  solubility  in 
alkalies. 
Sulphides  of  germanium  are  readily  formed  by  passing  vapors  of 
sulphur  over  germanium  at  a  red  heat.  Germanous  sulphide,  GeS, 
is  formed  by  heating  the  disulphide  with  an  excess  of  germanium  in 
a  current  of  carbonic  acid.  Germanic  sulphide,  when  heated  in  a 
slow  current  of  hydrogen,  yields  beautiful  crystals.  In  close  prox- 
imity to  the  heated  portion,  beautiful  thin  scales  or  feathery  crystals,, 
having  a  lustre  resembling  iodide  of  iron,  are  formed.  Held  up  to 
the  light,  they  are  transparent  with  a  bright-red  or  yellowish  color, 
and  form  a  brown-red  powder  when  pulverized.  When  heated  it 
fuses  and  volatilizes ;  heated  in  the  air,  it  is  converted  into  oxide. 
Solution  of  caustic  potash  dissolves  it  readily;  hydrochloric  acid  pre- 
cipitates amorphous,  reddish-brown  or  orange  sulphide ;  hot  concen- 
trated hydrochloric  acid  converts  it  into  germanous  chloride  (GeCl2). 
The  crystalline  sulphide  is  insoluble,  the  amorphous  sulphide  soluble, 
in  sulphide  of  ammonium  forming  disulphide.  Germanic  sulphide 
(GeS2)  is  prepared  by  precipitating  a  solution  of  germanic  oxide  with 
sulphuretted  hydrogen,  or  by  treating  its  sulpho-salts  with  an  excess 
of  acid,  whereby  a  voluminous  white  precipitate  is  obtained ;  it  is 
washed  with  dilute  acid  and  saturated  with  H2S.  The  acid  is  re- 
moved by  washing  with  alcohol  saturated  with  H2S,  then  with  ether, 
and  drying  in  vacuo.  Germanic  sulphide  is  quite  soluble  in  water; 
the  aqueous  solution,  however,  soon  decomposes,  emitting  H2S.  The 
dry  disulphide  soon  decomposes  when  exposed  to  a  moist  atmosphere, 
and,  as  a  consequence,  has  a  hepatic  odor.    Germanic  sulphide  is  a 
