NOTE  ON  OZONE. 
465 
of  an  ordinary  mirror.  It  is  remarkable  that  this  great  change 
in  the  state  of  the  mereury  is  not  accompanied  by  any  further 
diminution  of  the  volume  of  the  gas.  The  apparatus  employed 
by  the  authors  would  have  enabled  them  to  estimate  with  cer- 
tainty a  change  of  volume  amounting  to  — )0g  part  of  the  whole. 
On  the  contrary,  on  allowing  the  apparatus  to  stand,  the  gas 
begins  slowly  to  expand  ;  and  in  thirty  hours,  when  the  ozone 
reactions  have  disappeared,  the  expansion  amounts  to  a  little 
more  than  one-half  of  the  contraction  which  had  previously 
taken  place. 
Dry  silver,  in  the  state  both  of  leaf  and  of  filings,  has  the 
property  of  entirely  destroying  ozone",  whether  prepared  by  elec- 
trolysis or  by  the  electrical  machine.  If  a  stream  of  electrolytic 
ozone  be  passed  over  silver  leaf  or  filings  contained  in  a  tube, 
the  metal  becomes  altered  in  appearance  where  the  gas  comes 
first  into  contact  with  it ;  but  no  appreciable  increase  of  weight 
takes  place,  however  long  the  experiment  may  be  continued. 
The  volumetric  results  are  similar  to  those  already  described  in 
the  case  of  mercury. 
Arsenic  also  destroys  dry  ozone,  but,  as  it  likewise  combines 
with  dry  oxygen,  its  separate  action  on  ozone  cannot  be  observed 
with  precision. 
Most  of  the  other  metals  examined,  such  as  gold,  platina,  iron, 
zinc,  tin,  &c,  are  without  action  on  dry  ozone. 
Iodine,  brought  into  contact  with  oxygen  contracted  by  the 
electric  discharge,  instantly  destroys  the  ozone  reactions,  and  a 
yellowish  solid  is  formed :  no  change  of  volume  accompanies 
this  action. 
Peroxide  of  manganese  and  oxide  of  copper  have,  it  is  well 
known,  the  property  of  destroying  ozone,  apparently  without 
limit.  The  authors  have  found  that  these  oxides  undergo  no 
sensible  increase  of  weight,  even  after  the  destruction  of  50  or 
60  milligrammes  of  ozone.  The  same  oxides,  when  brought  into 
contact  with  oxygen  contracted  by  the  spark,  restore  it  to  nearly 
its  original  volume. 
Hydrogen  gas,  purified  with  care,  and  perfectly  dry,  was  not 
changed  in  volume  by  the  action  either  of  the  electrical  spark, 
or  of  the  silent  discharge. 
A  similar  negative  result  was  obtained  with  nitrogen  and  the 
