ON  PIPERINIC  ACID. 
427 
nitrate  of  ammonia  to  — 16-7°  C.  The  freezing  points  of  these 
solutions  are  — 2*8°,  — 2-0  and  — 16-7°,  respectively. 
If  500  grm.  of  sulphocyanide  of  potassium  is  dissolved  in  400 
c.c.  water  by  stirring  with  a  test  tube  half  filled  with  water,  this 
will  freeze  in  two  or  three  minutes.  This  salt  is  probably  best 
adapted  to  the  manufacture  of  ice. 
The  solubilities  in  the  above  table  are  taken  from  Mulder's 
statements.  With  the  two  sulphocyanides  the  author  experi- 
mented, and  found  in  100  parts  of  water  the  potassium  salt  solu- 
ble as  follows:  at  0°  177-2  p.,  at  20°  217-0  p.,  and  the  ammo- 
nium  salt  at  0°  122-1  p.,  at  20°  162-2  parts.— iV.  Jahrh.  J. 
Pharm.  1869,  April,  222—224,  from  Ber,  d.  d,  cJiem,  GesellsoL 
ii,  68. 
ON  PIPERINIC  ACID. 
Bt  Rud.  Fittig,  and  W.  H.  Mielck. 
The  acid  was  prepared  by  heating  piperina  with  alcoholic  so- 
lution of  potassa.  The  recrystallized  acid  fuses  at  216  to  217°  C. 
afterwards  constantly  at  212  to  213°  ;  v.  Babo  and  Keller  gave 
the  fusing  point  at  150°.  At  a  somewhat  higher  heat  the  acid 
partly  decomposes  and  sublimes  in  fine  yellow  needles.  Heated 
with  pure  water  to  235  or  245°  C.  it  is  completely  decomposed 
into  carbonic  acid  and  a  mixture  of  acid  resinous  bodies.  Ap- 
parently the  same  decomposition  is  effected  by  very  dilute  muri- 
atic acid  at  160°,  and  by  concentrated  muriatic  acid  at  100°. 
By  heating  with  lime,  it  yields  charcoal,  carbonic  acid,  water  and 
a  trace  of  oil  resembling  phenol.  Piperinate  of  potassa  heated 
with  iodide  of  ethyl,  potassa  and  alcohol,  yields  piperinic  ether. 
Chromic  acid  oxidizes  piperinic  acid  completely  to  carbonic  acid 
and  water.  With  dilute  nitric  acid,  oxalic  acid  and  a  red  amor- 
phous body  are  formed. 
Permanganate  of  potassa  oxidizes  the  piperinates,  the  solu- 
tion acquires  an  agreeable  odor  of  coumarin,  and  yields  by  dis- 
tillation a  beautifully  crystallizing  body,  piperonal  =  C8H2O3 ; 
oxalic  and  carbonic  acids  and  water  are  formed  at  the  same 
time.  Piperonal  crystallizes  from  water  in  long  lustrous  color- 
less transparent  prisms,  is  very  soluble  in  ether  and  boiling 
alcohol,  fuses  at  37°  C,  boils  at  263°  and  has  a  very  agreeable 
