SCHEELE  AND  HIS  DISCOVERIES. 
55 
sessed  a  peculiar  odor,  that  of  bitter  almonds ;  that  it  had  a 
burning  taste,  and  produced  coughing.  It  is  strange  that  he  did 
not  at  the  same  time  remark  its  poisonous  qualities.  Possibly 
his  very  manipulations  tended  to  shorten  his  life.  In  order  to 
assure  himself  of  its  composition,  he  treated  it  successively  with 
all  the  known  alkalis  and  acids.  When  found  he  called  it  sim- 
ply The  Coloring  Matter.  Bergmann  gave  it  the  more  ambi- 
tious title  of  Acidum  ccerulei  Berolinensis,  afterwards  styled 
Prussic  Acid  by  Guyton  de  Morveau,  and  finally  Hydrocyanic 
Acid  by  Gay  Lussac.  These  experiments  were  subsequently 
followed  up,  Scheele  continuing  to  study  the  action  of  this  col- 
oring matter  on  alka  i%  acids,  and  metals. 
He  established  that  Prussiate  of  Ammonia  might  be  entirely 
sublimed  ;  that  that  of  lime  yielded  its  base  to  caustic  alkalies  and 
acids ;  that   the  coloring  matter  was  capable  of  distillation. 
This  product  was  used  as  a  test  for  the  presence  of  iron,  and  he 
then  designated  it  as  Precipant  Liquor.    In  attempting  the  ele- 
mentary analysis  of  Prussic  Acid  he  at  first  supposed  that  it  was 
formed  of  Ammonia  and  Oil.    To  convince  himself  of  this,  he 
tried  every  possible  mixture  of  Ammonia  and  fatty  bodies, 
but  as  no  resulting  product  gave  Prussian  Blue  with  Sulphate 
of  Iron,  he  was  convinced  that  there  was  no  oil  in  its  composi- 
tion.   He  put  in  a  crucible  carbon  and  potash,  and  kept  them 
at  a  red-heat,  then  added  Sal  Ammoniac,  and  continued  the  heat 
until  no  more  ammoniacal  vapors  were  disengaged.    He  poured 
the  whole  into  filtered  water,  and  obtained  a  salt  (Prussiate  of 
Potash)   which  gave  a  dark-blue  precipitate  with  Sulphate  of 
Iron.    By  further  experiments  he  came  to  the  conclusion  that 
this  coloring  matter  was  composed  of  Ammonia,  Inflammable 
Air,  and  of  a  carbonaceous  substance.   These  three  bodies — Ni- 
trogen, Hydrogen,  and  Carbon,  are  in  fact  the  bases  of  Prussic 
Acid.    The  Annales  de  Chimie  de  Crell  (1784)  contain  five  me- 
moirs, one  being  specially  interesting  to  ourselves  as  Pharma- 
ceutists— .the  discovery  of  a  Sweet  Principle  obtained  from  Ex- 
pressed Oils  and  Animal  Fats.    He  obtained  it  by  boiling  one 
part  of  powdered  Litharge  in  two  parts  of  fat  with  a  little  water. 
This  is  the  ordinary  method  for  making  Emplastrum  Simplex. 
The  supernatant  liquor,  separated  by  decantation,  was  evapo- 
rated to  the  consistence  of  a  syrup.    This  substance,  of  a  sweet 
