554  Development  of  the  Chemical  Arts,  {^"''fcryt'"'' 
The  discovery  made  known  by  Schonbein,  according  to  which  the 
peculiar  phosphorous  odor  accompanying  the  electrolysis  of  water,  was 
due  to  the  evolution  of  oxygen  in  a  state  possessing  heightened  oxidiz- 
ing properties,  was  received  with  great  expectations,  both  in  medicine 
and  arts.  Schonbein  named  this  oxidizing  principle  ozone  (from  o^ecv^ 
to  smell),  and  he  perceived  its  evolution,  as  Van  Marum  had  already 
done  in  1785,  at  least,  as  far  as  the  odor  is  concerned,  near  the  con- 
ductor of  an  electric  machine  when  in  action.  He  discovered  subse- 
quently that  it  was  produced  also  during  the  slow  combustion  of  phos- 
phorus, and  that  it  was  present  in  the  atmosphere  in  very  preceptible 
traces.  Observations  of  its  occurrence  increased  very  rapidly.  Schon- 
bein and  others,  found  that  the  peroxides  of  silver,  barium  and  hydro- 
gen, in  contact  with  sulphuric  acid,  evolved  oxygen  more  or  less  strongly 
ozonized,  the  same  property  belonging  also  to  the  manganate,  per- 
manganate and  (according  to  Rammelsberg)  the  periodate  of  potash. 
The  agitation  of  air  with  mercury,  or  with  the  precious  metals  in  a 
state  of  fine  division,  or  with  powdered  glass,*  was  also  found  to  be  a 
means  of  ozonization.  The  ethereal  oils,  especially  oil  of  turpentine, 
display  this  property  in  a  high  degree.  Ozone  was  detected  in  the  air 
current  from  a  furnace -blast  and  in  the  oxygen  expired  by  plants. 
The  means  for  its  detection,  in  addition  to  the  fact  that  i  part  of 
ozone  imparts  its  peculiar  odor  to  500,000  parts  of  air,  were  found  in 
the  following  reactions  : 
Ozone  liberates  iodine  from  iodide  of  potassium,  iodic  acid  and  potas- 
sic  peroxide  being  simultaneously  formed,  and  the  solution,  after  the 
removal  of  the  iodine,  has  an  alkaline  reaction.  The  presence  of  the 
free  iodine  is  easily  demonstrated  by  means  of  moist  starch-paper,  and 
the  potash,  or  potassium  peroxide,  by  litmus.  Ozone  bleaches  indigo 
and  colors  freshly-prepared  tincture  of  guaiacum  a  deep  blue,  turns 
paper  brown  which  is  saturated  with  salts  of  manganous  oxide  or  thal- 
lous  salts  by  the  formation  of  higher  oxides,  oxidizes  mercury  at  ordi- 
nary temperatures,  and  converts  silver  into  black  silver  peroxide.  Paper 
saturated  with  thallous  oxide  and  exposed  to  ozone  blues  tincture  of 
guaiacum,  potassium-iodide  and  starch  before  it  turns  brown.  It  was 
sometimes  forgotten  that  the  reactions  with  indigo,  guaiacum  and  iodide 
of  potassium  and  starch  are  produced  also  by  chlorine,  nitrous  and 
hyponitrous  acid,  and  hence  phenomena  have  been  ascribed  to  ozone 
which  were  really  due  to  one  or  other  of  these  bodies. 
*  Andrew's  "  Nature,"  1875,  P*  S^S- 
