Note 36 tri — Chapter XVII · BORON, ALUMINIUM, AND THE ANALOGOUS METALS OF THE THIRD GROUP

In addition to the data given in Chapters XI., XIII., and in Chapter XV., Note 19, the following are the amounts of heat in thousands of units, evolved in the formation of the oxides and chlorides from the metals taken in gram-atomic quantities:

Na₂O 100; MgO 140*; ⅓Al₂O₃ 120*; ⅓Fe₂O₃ 63*;

Na₂Cl₂ 195; MgCl₂ 151; ⅓Al₂Cl₆ 107; ⅓Fe₂Cl₆ 64.

The asterisks following the oxides of Mg, Al and Fe call attention to the fact that the existing data refer to the formation of the hydrates of these metals, from which the heat of formation of the anhydrous oxides may easily be assumed, because the heat of hydration (for example, MgO + H₂O) has not yet been determined.