Calcium ferrite, magnesium ferrite and zinc ferrite, ROFe203(R=Ca, Mg, Zn), are obtained by intensely heating mixtures of the oxides; magnesium ferrite occurs in nature as the mineral magnoferrite, and zinc ferrite as franklinite, both forming black octahedra.
+Zn(n -I) a n_ 1= Zn(n+3) -2 (without which the transformation would be illusory); and the conclusion is that a 1, a 2, ...
Considering the curves of the order n which satisfy Zn(n+3) - 1 conditions, then the index N is the number of these curves which pass through a given arbitrary point.
FRANKLINITE, a member of the spinel group of minerals, consisting of oxides of iron, manganese and zinc in varying proportions, (Fe, Zn, Mn)"(Fe, Mn) 2"'0 4.
If U is the velocity of sound in a gas at pressure P with density p, and if waves of length X and frequency N are propagated through it, then the distanc?e l between the dust-heaps is 2 = N - zN Vyp' where y is the ratio of the two specific heats.