VOl. 75
NOTES
4346
allowed to fall t o -80" with the jacket a t atmospheric pressure. At this temperature, evacuation of the jacket space to 0.1 mm. gave slow cooling, with probable formation of solid 11, while evacuation to 100 mm. gave faster cooling, usually resulting in separation of solid I without detectable formation of solid 11. If the sample was allowed to supercool more than about l5', the halt corresponding to solid I1 was very brief, with a spontaneous rise in temperature a n d separation of solid I after a period of one-half t o 3 minutes. Such supercooling could be prevented by momentarily tilting the f.p. tube, causing the stirrer to rub against the side of the tube inducing initial formation of solid I1 crystals. From the available evidence, the change involved appears t o be monotropic, solid I1 being the metastable form. The fact that no conclusive evidence for complete solidification of the sample t o solid I1 has been obtained, and that no definite temperature is associated with the inception of change from solid I1 to solid I seems t o indicate that solid TI is continuously changing t o solid I at a finite rate. I t i i not t o be inferred that the rather sudden increase in temperature 2-7" below the f.p. of solid I1 necessarily corresponds to conversion of the solid I1 t o solid I , but morc probably that liquid remaining unfrozen in the necessarily unstirred sample is in contact with sufficient solid I to freeze directly to this form. DEPARTMENT OF CHEMISTRY \VEST VIRGINIACNIVERSITY ~IORGASTOWVN, \V, T'A.
body. 0n:this basis the N-fluoroacetyl derivatives have been prepared to test their effect on living cells and malignant tumors. Table I lists these new fluoroacetyl derivatives.
N-Fluoroacetyl Derivatives of Carcinogenic Amin e s
BY W D KUMLER' I
