table i averaee 't ' purification stage ( 12 obser- 't ' extremes % error vations ) as isolated -0.72 -0.25 ; -1.01 34.1 first recrystallization -0.95 -0.84 ; -1.09 9.8 second recrystallization -1.05 -0.99 ; -1.10 4.0 third recrystallization -1.11 -1.08 ; -1.13 1.8 fourth recrystallization -1.12 -1.10 ; -1.13 1.7 first resublimation -1.12 -1.11 ; -1.13 0.9 second resublimation -1.122 -1.12 ; -1.13 0.7 it is obvious from table i that for truly quantitative significance , thiotimoline purified as described must be used .