PIPERIC  ACID. 
139 
method  be  not  quite  successful,  the  solution  is  neutralized  by 
acetic  acid,  and  a  few  drops  of  acetate  of  lead  solution  is  added, 
which  produces  a  feeble  brownish  precipitate.  The  solution  is 
heated  to  boiling,  and  sulphuretted  hydrogen  passed  through,  to 
remove  traces  of  lead.  After  filtration  and  concentration,  the 
potash-salt  is  obtained  in  yellowish- white  crystals.  To  obtain 
the  acid,  these  are  dissolved  in  water,  and  decomposed  by  either 
sulphuric,  hydrochloric,  or  acetic  acid,  which  liberate  the  acid 
in  the  form  of  a  voluminous  gelatinous  precipitate,  which  is  seen 
under  the  microscope  to  consist  of  extremely  fine  needles.  The 
precipitate  is  collected  on  a  filter,  washed,  and  then  dried  in 
vacuo  over  sulphuric  acid.  On  crystallization  from  alcohol  it 
forms  fine  interwoven  needles  of  a  yellowish  color  which  is  pecu- 
liar to  them. 
The  acid  is  almost  insoluble  in  water,  readily  soluble  in  boil- 
ing absolute  alcohol,  from  which  it  crystallizes  on  cooling.  It 
melts  at  302°  and  sublimes  at  392°  F. :  a  brown  residue  remains, 
and  the  sublimate  has  the  odor  of  cumarine.  The  acid  scarcely 
reddens  litmus,  but  forms  with  bases  well-characterized  salts. 
Treated  with  weak  nitric  acid,  piperic  acid  forms  an  orange- 
colored  nitro-compound.  By  sulphuric  acid  it  is  decomposed 
with  formation  of  the  violet  color  characteristic  of  piperine  when 
similarly  treated.  With  chlorine,  iodine,  and  bromine  substitu- 
tion products  are  obtained,  which  await  investigation.  With 
pentachloride  of  phosphorus,  it  yields  oxychloride  and  a  sub- 
stance which  is  deposited  in  vermilion-colored  crystals. 
The  analysis  of  the  acid  gave — 
I.  II.  III.  IV. 
C  =66-88       66-08       66-74  66-39 
H       4-80        4.83        5-06  5-14 
0     28-32      29-09      28-20  28.47 
From  these  results  the  formulae  may  be  calculated  : — 
C  50=300  66-37      C  50=300   66-67      C  26=156  67-24 
H  24     24     5-31      H  22     22    4-89      H  12     12  5-17 
O  16    128  28-32      O  16    128   28-44      O  18     64  27-50 
The  formation  of  piperic  acid  may  be  expressed  by  the  follow- 
ing equation  : — 
C70  H40N2  012+4HO=2(C10  H11  N)+C50  H22  O16 
Piperine.  Piperidine.       Piperic  acid. 
