260 
POPULIN. 
composed  with  production  of  saligenin,  lactic  acid,  and  benzoate 
of  lime. 
Among  the  three  substances  supposed  by  Piria  to  exist  in  pop- 
ulin  ;  saligenin  and  grape  sugar  have  been  recognized  as  con- 
stituents of  salicine  ;  so  that  there  was  reason  to  suppose  popu- 
lin  might  be  converted  into  salicine  by  separation  of  the  ben- 
zoic acid.  This  was  found  to  be  the  case  when  populin  is  boiled 
with  baryta  water  or  milk  of  lime.  In  order  to  obtain  the  sali- 
cine, the  benzoic  acid  is  precipitated  by  means  of  perchloride  of 
iron,  excess  of  iron  removed  by  lime,  and  excess  of  lime  by  car. 
bonic  acid.     The  liquid  then  yields  salicine  on  evaporation. 
Piria  found  the  quantity  of  benzoic  acid  yielded  in  this  way  to 
be  28.90  per  cent.  This  corresponds  with  the  view  he  holds  of 
its  composition,  which  would  require  26.68  per  cent. 
The  salicine  thus  obtained  is  identical  in  all  respects  with  the 
natural  salicin,  its  composition  being  represented  by  the  for- 
mula C,0  H18  Ou 
The  conversion  of  populin  into  salicin  may  be  effected  even 
by  heating  it  with  an  alcoholic  solution  of  ammonia  to  212°  F. 
Weak  nitric  acid  acts  upon  it  only  at  212  F.,  forming  a  yel- 
low  solution  which,  after  long  boiling,  evolves  vapor  having  the 
odor  of  hydruret  of  salicyle.  When  heated  with  ordinary  ni- 
tric acid,  populin  is  probably  converted  into  nitrobenzoic  acid 
and  oxalic  acid. 
By  the  action  of  nitric  acid,  1.-30  s.  g.,  populin  is  converted 
into  a  substance  which  Piria  calls  benzohelicin.  The  substance 
has  great  analogy  with  helicin  ;  it  crystallizes  in  silky  needles  ; 
sulphuric  acid  dissolves  it  with  yellow  color,  and  the  solution, 
when  diluted  with  water,  evolves  hydruret  of  salicyle.  The  same 
substance  is  formed  by  boiling  with  hydrochloric  acid  with  sepa. 
ration  of  benzoic  acid.  In  the  cold,  caustic  alkalies  do  not  alter 
benzohelicin,  but  at  212°  F.  it  dissolves  with  intense  gold  yellow 
color,  yielding  the  same  products,  together  with  grape  sugar, 
when  the  alkaline  solution  is  neutralized  by  an  acid. 
The  constitution  of  this  substance  would  appear,  therefore,  to 
be  analogous  to  that  of  populin.  Its  composition  is  represented 
by  the  formula  C_,0  H20  016.  by  heating  it  does  not  lose  water. 
The  above  decomposition  may  be  represented  by  the  equation : 
