SCHEBLE  AND  HIS  DISCOVERIES. 
51 
amination  of  Fluor  Spar  and  its  Acid."  Some  years  previous, 
Margraff  was  engaged  on  the  same  subject,  and  pointed  out  thac 
Fluor  Spar  did  not  contain  Sulphuric  Acid.  Scheele,  on  treat- 
ing it  with  this  powerful  reagent,  noticed  certain  white  acid  va- 
pors which  attacked  the  glass.  He  named  this  product  FIuo- 
silicic  Acid.  Remarking  that  the  vessel  filled  with  water  in 
which  it  was  collected  was  covered  with  a  coating  of  Silica,  he  at 
first  thought  that  Silica  was  composed  of  Water  and  Fluoric 
Acid ;  but  in  a  second  notice  (1780)  he  recognized  his  mistake, 
and  demonstrated  that  the  Silica  obtained  came  from  the  glass 
of  the  retort  or  else  from  the  receiver.  The  ultimate  result  of 
this  investigation  was  the  admission  of  the  radical  called  Fluor. 
In  1774  Scheele  published  his  " Researches  on  Black  Magnesia," 
otherwise  called  Manganese.  He  was  then  living  at  Upsal,  for 
it  wa3  at  the  instigation  of  Bergmann  that  he  undertook  this  in- 
quiry— one  of  his  best  performances.  This  memoir  contains  no 
less  than  four  discoveries,  which  would  have  sufficed  to  have  es- 
tablished the  reputation  of  a  skilful  chemist.  In  the  first  place, 
he  discovered  that  this  ore  combined  eagerly  with  metallic  ox- 
ides and  with  some  acids,  whence  he  concluded  that  black  Mag- 
nesia had  a  metallic  base.  On  treating  it  successively  with  all 
the  strong  acids,  he  remarked  (1)  That  with  Sulphuric  Acid  he 
obtained  a  white  pinkish  salt  (Sulphate  of  Manganese),  and 
that  there  was  liberated  an  elastic  fluid  which  was  not  fixed  air, 
the  only  gas  then  known,  but  which  possessed  the  properties  of 
dephlogisticated  air,  being  evidently  oxygen.  (2)  With  Muriatic 
Acid  he  produced  a  gas  of  yellow  color,  having  an  odor  of 
Aqua  Regia.  Having  collected  this  gas  in  a  bladder,  it  was 
colored  yellow,  from  which  he  at  first  thought  that  it  was  Aqua 
Regia  in  a  state  of  vapor.  He  then  collected  it  in  bottles 
filled  with  water,  with  Hale's  apparatus,  and  he  noticed  that  the 
gas  corroded  the  corks  and  turned  them  yellow  ;  that  it  bleached 
blue  Litmus  Paper  as  well  as  vegetable  colors,  and  that  during 
this  action,  in  presence  of  water,  the  gas  was  converted  into 
Muriatic  Acid.  He  also  established  that  plants  once  thus 
bleached  did  not  recover  their  natural  colors,  neither  on  the 
addition  of  Acids  or  Alkalis ;  that  this  gas  attacked  all  metals. 
In  a  word,  he  gave  an  exact  and  complete  history  of  this  new 
gas,  which  at  first  he  called  Dephlogisticated  Muriatic  Acid, 
