52 
SCHEELE  AND  HIS  DISCOVERIES. 
which  since  has  heen  termed  Oxygenated  Muriatic  Acid  Gas, 
and  to  which  has  been  recently  given  the  appellation  of  Chlorine. 
A  third  discovery  made  by  Scheele  in  studying  Manganese 
was  Baryta,  with  which  it  is  nearly  always  associated.  He 
showed  that  this  new  Earth,  which  he  called  Terre  pesante 
heavy),  is  distinct  from  Lime  and  Silica ;  that  it  neutralizes 
acids,  and  forms  with  Sulphuric  Acid  and  the  Sulphates  a  neu- 
tral salt  insoluble  in  water.  Fused  with  Borax  it  forms  a  vit- 
reous mass,  which  is  colored  brown  on  the  addition  of  a  little 
Sulphur,  etc. 
Lastly,  he  remarked  that  Ammonia,  treated  by  Nitrate  of 
Manganese,  is  decomposed,  producing  a  gas  differing  from  Car- 
bonic Acid,  namely,  Nitrogen.  Considering  that  this  disserta- 
tion on  Manganese  was  published  in  1774,  and  that  the  experi- 
ments on  which  it  is  based  went  back  for  several  years,  Scheele 
may  be  regarded  as  having  been  the  first  to  discover  Nitrogen 
gas,  which  he  for  a  long  time  called  Vitiated  or  foul  air  [Air 
vicie  ou  corrompu). 
Next  year  (1775)  Scheele  read  before  the  Academy  of  Stock- 
holm his  Remarks  on  the  Salt  of  Benzoin,  Up  to  this  time 
Flowers  of  Benzoin,  already  recognized  as  an  acid,  were  ob- 
tained by  means  of  sublimation.  Scheele  used  the  wet  way, 
which  gave  a  better  and  more  abundant  product.  After  boiling 
powdered  Benzoin  with  quicklime,  he  filtered  the  solution  and 
added  Muriatic  Acid.  Benzoic  Acid  was  precipitated  in  beauti- 
ful crystalline  plates,  of  a  strong  odor  when  exposed  to  heat. 
This  ingenious  and  convenient  process  has  been  followed  ever 
since.  [A  most  successful  though  unfortunately  secret  process 
was  adopted  by  Mr.  Fowler,  of  Bedford  Street,  Covent  Garden. 
Since  his  death  his  method  has  apparently  been  lost.  No  Flow- 
ers of  Benzoin  with  which  I  am  acquainted  are  free  from  a  cer- 
tain empyreumatic  odor,  varying  in  different  commercial  sam- 
ples, but  always  present. — J.  I.] 
The  same  year  Scheele  published  one  of  his  most  important  * 
discoveries, — a  paper  on  Arsenic  Acid.  He  imagined  that  White 
Arsenic  {the  Arsenious  Acid  of  Fourcroy)  could  take  two  de- 
grees of  acidity.  He  treated  crude  arsenic  with  Nitrous  Acid, 
and  obtained  Arsenic  Acid ;  he  examined  all  its  combinations 
with  the  alkalis  and  metals ;  he  demonstrated  that  combustible 
