350  The  Violet  Perfume. 
July,  1695. 
melts  without  decomposition.  Its  trimethyl  ester  forms  compact 
crystals  of  M.  P.  I27c-I28c. 
(d)  loniregenetricarboxylic  Acid : 
CH,  CH3 
,C  —  COOH 
HOOaC6H3<f 
xCOOH 
This  acid  is  always  produced  as  the  final  oxidation  product  of 
Irene,  when  this  operation  is  carried  out  at  first  by  gentle  and  then 
by  more  powerful  oxidizing  agents.  It  crystallizes  in  white  needles, 
and  is  slightly  soluble  in  cold  water,  alcohol  or  ether,  but  is  solu- 
ble in  these  reagents  when  they  are  hot,  and  is  not  dissolved  by 
benzol  or  ligroin.  At  150°  it  loses  a  molecule  of  water,  and  is  con- 
verted into  the  anhydride.  The  salts  of  the  acid  crystallize  well 
The  acid  is  stable,  and  is  not  altered  by  oxidizing  agents  or  by 
warm  concentrated  H2SOr    The  anhydride 
/C0V 
CSHP— CO/ 
XCOOH 
crystallizes  from  benzol  in  plates  of  M.  P.  214°,  and  maybe  dis- 
tilled without  decomposition.  The  trimethyl  ester  of  the  acid  crys- 
tallizes from  warm  ligroin  in  colorless  needles  of  M.P.  93°. 
Imid  acid  of  loniregenetricarboxylic  Acid : 
CO 
NH 
QH—  CO. 
^  XCOOH 
This  imid  acid  is  produced  when  the  NHA  salt  of  ioniregenetricar- 
boxylic  acid  is  dry,  distilled  in  a  current  of  C02  gas.    It  is  a  white 
crystalline  powder,  which  is  insoluble  in  the  usual  solvents,  M.  P. 
over  300°,  and  boils  a  few  degrees  higher  than  this. 
Its  Ag  salt 
/C0X 
/  >NH 
C  H— CO/ 
XCOOAg 
is  a  white  powder  which,  when  heated  in  a  current  of  C02,  yields 
the  imid  of  dimethylhomophthalic  acid 
