AmM^rch)f819frm,}  Action  of  Sulphuric  Acid  upon  Wood-Charcoal.  151 
liquid,  carries  down  with  it  the  chief  part  of  the  brown  products. 
On  continuing  this  fractionation  until  the  liquid  becomes  alkaline, 
we  obtain  five  precipitates  less  and  less  deeply  colored.  The  two 
first  are  crystalline,  the  three  latter  gelatinous. 
Leaving  for  the  present  the  three  last  amorphous  precipitates,  as 
well  as  the  barium  salt  which  remains  in  solution  in  the  ultimate 
alkaline  liquid,  I  will  merely  now  examine  the  two  crystalline  pre- 
cipitates, which  are  similar  enough  to  be  united  together. 
They  give,  in  dilute  HC1,  a  brown  solution,  which  on  concentra- 
tion deposits  an  acid  barium  salt  crystallized  in  needles  mixed  with 
barium  chloride.  These  two  salts  are  easily  separated  from  the 
brown  products,  and  they  are  obtained  quite  white  after  three  or 
four  recrystallizations  in  dilute  HC1.  They  are  then  decomposed  by 
equivalent  quantity  of  sulphuric  acid.  The  barium  sulphate  is  fil- 
tered off,  the  liquid  evaporated  to  dryness  to  expel  hydrochloric 
acid,  and  the  residue,  on  a  final  crystallization  from  water,  yields  pure 
pheno-pentamethyloic  acid.  The  yield  is  three  per  cent,  of  the 
weight  of  the  charcoal  used.  This  acid,  first  obtained  by  Friedel 
in  1880,  by  oxidizing  pentamethylbenzene  by  means  of  potassium 
permanganate  is  very  soluble  in  hot  water,  from  which  it  is  depos- 
ited in  fine  silky  needles.  It  is  soluble  in  alcohol  and  ether ;  it 
effloresces  in  the  air,  and  loses  27- 56  per  cent,  of  water  over  sul- 
phuric acid.  The  quantity  of  water  calculated  for  C6H(C02H)56H20 
reaches  26-60  per  cent. 
If  dried  at  I  io°  it  agrees  with  the  formula  C6H(C02H5).  On  sat- 
uration with  ammonia  it  precipitates  barium  chloride  ;  like  the  cor- 
responding mellate,  the  amorphous  precipitate  is  not  spontaneously 
converted  into  crystals.  Its  alkaline  salts  give,  with  silver  nitrate, 
a  precipitate  which  on  desiccation  contains  64-38  per  cent,  of  silver. 
This  salt  deflagrates  if  heated,  yielding  a  black  voluminous  pulveru- 
lent matter,  which  on  roasting  leaves  a  moss  of  pure  silver. 
This  acid  requires  for  saturation  93-46  per  cent.  KOH.  These 
data  suffice  to  characterize  pheno-pentamethyloic  acid. 
To  complete  this  investigation  it  remains  for  'me  to  purify  the 
fractionation  baryta  products,  which  I  have  not  yet  been  able  to 
examine,  and  to  determine  if  the  acids  just  described  are  really 
derived  from  carbon,  or  if  they  are  merely  the  results  of  hydrogen 
products  which  an  incomplete  calcination  always  leaves  in  wood- 
charcoal. 
