Aja^uaryPih9wm'}         Constitution  of  the  Alkaloids.  13 
The  latter,  or  Liebig's  amidogen  theory,  assumed  that  all  alka- 
loids contained  the  radical  amidogen  NH2  and  that  they  were  really 
ammonia  in  which  one  hydrogen  atom  was  replaced  by  an  electro- 
positive radical  which  was  different  for  each  alkaloid.  This  was  in 
1 842.  Both  of  these  were  merely  the  views  or  the  theories  of  these  two 
chemists.  The  first  step  in  the  illuminating  of  the  ways  was  made 
by  A.  W.  von  Hofmann,  a  pupil  of  Liebig,  and,  strange  to  say,  an 
adherent  of  the  Berzelius  alkaloid  theory.  It  was  in  1843  that  Hof- 
mann began  his  famous  work  on  the  substance  aniline,  which  served 
the  chemical  world  a  twofold  purpose — first,  in  establishing  the  ani- 
line industry;  and,  secondly,  in  disproving  the  Berzelius  alkaloid 
theory  and  establishing  the  Liebig  theory  of  the  constitution  of 
these  compounds.  Unverdorben  had  in  1826  obtained  a  substance 
he  called  "  Krystallin  "  by  the  dry  distillation  of  indigo,  and  later, 
in  1840,  Fritzsche,  by  distilling  indigo  with  caustic  potash,  had  ob- 
tained a  substance,  an  oil,  which  he  named  aniline.  Zinin,  about 
the  same  time,  obtained  a  substance  he  named  "  Benzidam,"  by 
the  action  of  ammonium  sulphide  on  nitrobenzene.  You  will  note 
that  I  use  the  terminology  ene  for  aromatic  hydrocarbons,  and  not 
ole,  as  I  frequently  observe  is  done,  and  as  is  given  in  the  U.S. P. 
Old  and  new  teachers  of  chemistry  give,  as  far  as  I  know,  the 
names  benzene,  toluene,  xylene,  etc.,  to  these  substances,  and  not 
benzole,  toluole,  xylole,  etc.,  as  the  termination  ole  or  ol  is  to  be,  and 
always  has  been,  as  far  as  I  know,  reserved  for  substances  of  an 
.alcoholic  nature,  such  as  carbinol,  phenol,  resorcinol,  etc.,  i.  e.y  such 
substances  as  contain  hydroxyl.  Hofmann,  in  1843,  fractionally 
distilled  the  heavy  oil  from  coal  tar,  and  obtained  a  colorless  oil, 
which  he  called  cyanol,  and  which  he  showed  was  identical  with 
the  krystallin,  aniline  and  benzidam  just  mentioned.  He  tried  the 
action  of  cyanogen  upon  aniline,  and  obtained  cyananiline,  cyano- 
diphenyl-diamine,  or,  as  he  called  it,  melaniline  and  dicyan-melani- 
line,  all  bases  and  addition  products.  He  still  thought  that  his 
work  so  far  demonstrated  the  correctness  of  Berzelius*  view  of 
conjugated  compounds,  and  he  writes  these  compounds  NH3.C6H4, 
equivalent  to  aniline  ;  NH3.C6H4.CN  equivalent  to  cyananiline,  etc. 
He  now  tried  to  split  up  aniline  into  ammonia  and  phenyl,  its  two 
conjugated  radicals,  but,  of  course,  failed.  He  next  applies  a  rigorous 
test  to  the  Berzelius  theory  by  studying  the  action  of  phosphorus 
pentoxide,  a  powerful  dehydrating  agent,  upon  oxanilide,  arguing 
