Wasserfreies Eisen(III)sulfat, Fe
2(SO
4)
3, existiert in zwei Modifikationen. Nach Einkristallaufnahmen kristallisiert die eine wahrscheinlich in Raumgruppe
C3i2 - R[`3]C_{3i}^2 - R\bar 3
(a
rh=8,791±0,004 Å,
C3i2 - R[`3]C_{3i}^2 - R\bar 3
(a
rh=8.791±0.004 Å,
=55°52
±2
; Z=2), whereas the other in space group C
2h
5
–P2
1/n (a=8.296±0.002 Å, b=8.515±0.002 Å, c=11.60±0,002 Å,
=90°30
; Z=4). The lattice constants of the rhombohedral modifications of Cr
2(SO
4)
3 and Ga
2(SO
4)
3, which are isomorphous with rhombohedral Fe
2(SO
4)
3, have been determined from powder photographs.
Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.