A MASS SPECTROMETRIC STUDY OF SUBLIMATION OF MANGANESE

The absolute sublimation pressure of manganese has been determined as a function of temperature over the range 1197°-785°K by a combination of mass spectrometric and effusion techniques which provides an internal pressure calibration. At 298°K ΔHsubl[Mn(α, s)] = 66·45±0·4 kcal mole-1 by the third law method and 65·78±1·0 kcal mole-1 by the second law method. From 1200° to 990°K, the β{rightwards paired arrows}α transition temperature, the vapor pressure of Mn is given by R ln P= 67,640 ± 400 T - 3·36 ln T -0·33 × 10-3T+ 57·46±0·3. From 990° to 780°K the equation becomes R ln P= 66,896 ± 400 T - 0·73 ln T -3·38 × 10-3T+ 39·63±0·4. The literature data are compared and the stabilities of MnF(g) and MnF2(g) are recalculated. © 1969.