Dehydration of goethite and diaspore*
Abstract
The dehydration of goethite and diaspore is studied in detail by single-crystal and powder x-ray methods, and also by the use of the electron microscope. By variation of the temperature of dehydration and duration of heating it has been possible to observe intermediate states in the process.
These intermediate states are revealed by satellite reflections which at certain temperatures occur close to the developed hematite or corundum diffraction spots. At higher temperatures these satellites are replaced by diffuse intensity regions, which disappear on further heating. The satellites could correspond to a sinusoidal structure-amplitude modulation along the c axis of the hematite or corundum crystallites, before dehydration is complete. The wavelength of the modulation was 32 Å for the hematite formed from goethite, and 39 Å for the corundum formed from diaspore.
Non-uniform broadening of the lines on powder photographs of the developed hematite, or corundum, was observed only when the original goethite or diaspore showed a particular texture. This effect is ascribed to stacking faults.
A well developed system of pores was observed on heated diaspore. The activation energies involved in the dehydration have been determined (19.8 kcal/mole for goethite, and 24.1 kcal/mole for diaspore). The inhomogeneous mechanism is confirmed for this type of dehydration, and a structural explanation for the formation of the satellites is presented.
Artikel in diesem Heft
- Structure defects in kaolinite
- Dehydration of goethite and diaspore*
- Contributions to the crystal chemistry of normal and defect tetrahedral structures*
- The crystal and molecular structure of a synthetic imidazo-purine
- The crystal structure of the anhydrous cadmium and mercuric sulfates
- The crystal structure of dimethyl sulfone
- Hydrogen bonding and conformations in echitamine salts
- Ein einfacher Heizaufsatz für die Präzessionskamera
- Röntgenaufnahmen mit der Buergerschen Präzessionskamera bei Temperaturen zwischen 1000°C und 2000°C
- Die Kristallstruktur des Phenols
- Crystal structure of bis-(hydrazine)manganese(II) chloride
- On the crystal structure of biotites
- A three-dimensional refinement of crystalline structure of trioxane*
- Über die Orientierung des durch Erhitzen aus Manganit entstehenden Pyrolusits
Artikel in diesem Heft
- Structure defects in kaolinite
- Dehydration of goethite and diaspore*
- Contributions to the crystal chemistry of normal and defect tetrahedral structures*
- The crystal and molecular structure of a synthetic imidazo-purine
- The crystal structure of the anhydrous cadmium and mercuric sulfates
- The crystal structure of dimethyl sulfone
- Hydrogen bonding and conformations in echitamine salts
- Ein einfacher Heizaufsatz für die Präzessionskamera
- Röntgenaufnahmen mit der Buergerschen Präzessionskamera bei Temperaturen zwischen 1000°C und 2000°C
- Die Kristallstruktur des Phenols
- Crystal structure of bis-(hydrazine)manganese(II) chloride
- On the crystal structure of biotites
- A three-dimensional refinement of crystalline structure of trioxane*
- Über die Orientierung des durch Erhitzen aus Manganit entstehenden Pyrolusits
