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The standard heat of formation of chlorine trifluoride (gas) at 298.15 K has been determined to be - 164.65 kj mol -1 (-39.35 kcal mol -1 ) with an overall experimental uncertainty of 5.14 kj mol -1 (1.23 kcal mol -1 ). This value is derived from the enthalpies of the following reactions which were measured directly in a flame calorimeter operated at 1 atm pressure and 303.5 K, together with data from previous investigations. ClF 3 ( g ) + 2 H 2 ( g ) + 100 H 2 O ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) ( 1 / 2 ) Cl 2 ( g ) + 1 / 2 H 2 ( g ) + [ 3 HF ⋅ 100 H 2 O ] ( 1 ) → [ HC 1 ⋅ 3 HF ⋅ 100 H 2 O ] ( 1 ) The enthalpy of formation of [HC1‧100H 2 O](l) was also measured. The average Cl - F bond energy in chlorine trifluoride is calculated to be 160.1 kj mol -1 (38.26 kcal mol -1 ).

An electron microscopic investigation was made of the origin and morphology of the canal system that connects sister spermatocytes of larval Bombyx mori. Canal formation results from incomplete cleavages during the mitoses which immediately precede meiosis. We suggest the lip which surrounds each canal is derived from the contractile ring which is prevented from constricting completely by interaction with the midbody. Cells were found with as many as four canals which demonstrates that canal rims can persist through a number of mitotic cycles. Speculations are advanced as to the significance of these canals in restricting gonocytes from unlimited divisions., (Copyright © 1971 Wiley-Liss, Inc.)