Patent ID: 8063092

Claim:
A process for preparing crystalline modification II of fipronil which has an X-ray powder diffractogram showing, at 25° C., at least 5 of the following reflexes: (1) d=13.44±0.2 Å (2) d=7.84±0.1 Å (3) d=5.50±0.07 Å (4) d=5.14±0.05 Å (5) d=4.95±0.05 Å (6) d=3.95±0.05 Å (7) d=3.77±0.05 Å (8) d=3.22±0.03 Å (9) d=2.91±0.03 Å comprising: i) preparing a solution of a solid form of fipronil being different from the crystalline modification II in a solvent S selected from tetrahydrofuran and 1,2-dichloroethane; ii) effecting crystallization of fipronil; and iii) isolating the resulting precipitate.