Mossbauer effect measurements for a series of iron compounds of the type Ca,Fe3-,0, (0 4 z 5 0.55), known as calcium-magnetites, are performed a t room temperature and liquid nitrogen temperature. A single calcium-magnetite phase giving Mossbauer spectra with magnetite-like Zeeman splitting was observed up fo z m 0.28. For higher Ca concentrations a second phase, represented by the additional quadrupole doublet, waa detected. This new phase may be identified as CaFe,O, ferrite. MoQbauereffektmeasungen wurden fur eine Reihe von Eisenverbindungen dea Typs Ca,Fe)-,O, (0 5 z 5 0,55), die als Kalzium-Magnetite bekannt sind, bei Zimmertemperatur und bei der Temperatur des flussigen Stickstoffs durchgefiihrt. Bis zu z w 0,28 wurde eine einzige Kahium-Magnetitphase beobachtet, die MoQbauerspektren mit einer Zeeman-Aufspaltung wie Magnetit ergab. Fur hohere Ca-Konzentrationen wurde eine zweite Phase durch ein zusiitzlicheaQuadrupo1-Dublett nachgewiesen. Diese neue Phase kann als CaFe,O,-Ferrit identifiziert werden.

Summary. :For the estimation of the properties of calcium-iron olivines in ironore sinters, synthetic mixtures of CaO, FeO, and SiO2 were prepared and melle.'t ; the obtained olivines were then examined microscopically and by X-ray powder method. The investigations allowed to state, that with the increase of the basicity of sinters, the relation of Fe : Ca in olivines decreases, which causes the change of their physical, optical, and rSntgenometric properties. THE chemical composition and melting temperatures of calciumiron olivines are presented in the diagrams (CaO-FeO-Si02 and Fe2SiO4-CasSi04) of N. L. Bowen, J. F. Schairer, and E. Posnjak (1932, 1933). From these diagrams it is apparent that calcium-iron olivines form solid solutions with limited solubility. The extreme member fayalite Fe2SiO 4 has a melting temperature 1205 ~ and the extreme member with the highest amount of calcium contains 42 ~o Fe2Si04 and 59 % CazSiO 4 by weight. Calcium-iron olivines are the chief component of the silicate phase in iron-ore sinters, strongly influencing the reducibility and strength of self-fluxing sinters. Synthesis. The varying chemical composition of olivines in iron-oresinters necessitated an investigation of the mineralogical characteristics of calcium-iron olivines. Therefore a number of syntheses of olivines were carried out at a temperature above the melting point, using pure components CaO, FeO, and Si02; FeO was obtained by the dissociation in vacuum of ferrous oxalate, Fe(C~Oa). 2HsO. The samples were melted in pots made of armco-iron in vacuum or in argon. The assumed and actually obtained analyses of synthetic olivines are presented in table I. From the figures in this table it is apparent that the passing of some FeO into FeaO 4 could not be avoided. The presence of FeaO a has been confirmed by microscopic examination; Bowen, Schairer, and Posnjak found 2"0 to 2"8 ~o Fe20s in their silicate melts.Optical properties of synthetic calcium-iron olivines. These olivines are characterized by a dark eolour, from dark green or brown for fayalite

Mössbauer measurements were performed at room temperature for a group of nonstoichiometric iron oxides of the Fe1‐xO type with 0.002≦x≦0.250. The measured spectra for the samples with x ranging from 0.002 to 0.083 represent quadrupole split Fe2+ doublets and an unseparated Fe3+ singlet. For the samples with x≧0.084 apart from asymmetric quadrupole splitting, a double Zeeman splitting appears, due to the formation ofmagnetite‐like clusters. The intensity ratio of the quadrupole pattern of the wüstite phase to the Zeeman pattern of the magnetite phase decreases with increasing x to zero for x = 0.250 (pure synthetized magnetite), which is in agreement with X‐ray diffraction analyses.

Untersuchungen zur Reduzierbarkeit und Festigkeit von Sintern mit verschiedenem Basengrad im Bereich von CaO/SiO2 = 0,38 bis 2,20 sowie mit verändertem Eisen(II)‐oxidgehalt von 6 bis 16%. Mineralogischer Aufbau der Sinter sowie Abhängigkeit der Textur und des Phasenbestandes von Basengrad und Eisen(II)‐oxidanteil. Änderungen von Mineralbestand und Textur nach der Reduktion bei 950 °C und nach schwach reduzierender Behandlung bei 500 °C.

Mössbauer absorption measurements for a series of calcium–iron olivines of the type (Fe1–xCax)2SiO4 with 0 ≦ x ≦ 0.65 were performed at room temperature and 500 K. The observed jump of the quandrupole splitting near x = 0.40 is attributed to a change of the crystalline. field.