ACTION  OP  SULPHUR  ON  AMMONIA.  25 
the  latter  by  evaporation,  and  of  cadmium  by  sulphuretted  hy- 
drogen, the  filtrate  gives  with  lead  a  pure  white,  and  with  silver 
a  white  precipitate  turning  black.  This  reaction  was  observed 
after  five  months,  but  ceased  to  be  produced  after  another 
month.  Pentathionic  acid,  which  might  likewise  have  been 
formed,  precipitates  silver  salt  yellow. 
The  experiment  with  flowers  of  sulphur  was  repeatedly  made. 
The  wash-water,  after  careful  concentration  in  a  water-bath, 
yields  with  absolute  alcohol  a  precipitate  of  a  little  gypsum  and 
sulphate  of  ammonia  ;  by  the  addition  of  ammonia,  some  ferric 
oxide  is  frequently  precipitated.  If  this  is  omitted,  and  the 
evaporation  continued  to  dryness,  the  hyposulphurous  acid  will 
be  decomposed  by  the  free  sulphuric  acid,  which  likewise  black- 
ens the  residue  from  the  presence  of  some  organic  impurities, 
and  lime  evolves  ammonia,  so  that  flowers  of  sulphur  must  con- 
tain a  small  proportion  of  an  ammoniacal  salt. 
Hyposulphurous  acid  may  frequently  be  detected  even  in  well 
washed  flowers  of  sulphur,  also  in  sublimed  or  precipitated  sul- 
phur after  crystallization  from  bisulphuret  of  carbon  ;  even  roll 
sulphur  is  not  free  from  it  and  sulphuric  acid,  so  that  absolute 
purity  of  sulphur  is  not  easily  attained. 
The  hyposulphurous  acid  S202,  being  the  lowest  oxide,  may 
probably  originate  by  direct  oxidation  ;  the  author,  however,  has 
been  unable  to  obtain  it  by  exposing  pure  sulphur  to  ozone 
(from  KO,  Mn207,)  and  to  chlorine  water,  by  slowly  burning 
sulphur  in  a  moist  atmosphere,  by  evaporating  water  from  it  for 
several  days,  and  by  the  spontaneous  decomposition  of  solution 
of  sulphuretted  hydrogen.  Still,  it  is  possible  that  these  ex- 
periments were  undertaken  on  too  small  a  scale,  or  not  continued 
sufficiently  long. 
Hyposulphites,  if  searched  for,  will  probably  be  frequently 
detected  in  natural  products.  Until  now,  hyposulphurous  acid 
has  been  discovered  only  by  Fellenberg,  in  1849,  in  the 
water  of  the  Gurnigel,  in  Switzerland,  by  Pe'ligot,  in  the  cele- 
brated spring  of  Grrenelle,  and  by  Wittstein,  in  1857,  in  the 
sulphur  spring  of  Alle  Prese,  near  Poschiavo. 
Distilled  water,  enclosed  with  pure  sulphurous  acid  and  milk 
of  sulphur  in  a  sealed  glass  tube,  and  heated  for  several  days  to 
between  80  and  90°  C,  contains  hyposulphurous  acid  ;  the  same 
