Crystal Growth in Magnetic Fields (II) Crystallization of Co(NH₄)₂(SO₄)₂ · 6 H₂O from Aqueous Solutions in High Magnetic Fields

Abstract

Crystal Growth in Magnetic Fields (11)Crystallization of CO(NH&(SO~)~ . 6 HzO from Aqueous Solutions in High Magnetic FieldsThe displacement rate of (110) single crystal faces of Co(NH,),(SO,), 6 H,O has been measured in dependence on the supersaturation of aqueous solutions in the zero field and at magnetic flux densities of 7 T. The results show that in a given external field measurable effects near the equilibrium don't occur (thermostatic field effect). On the contrary a marked influence at extreme relative supersaturations can be observed (kinetic field effect).Die Verschiebungsgeschwindigkeit der ( 110 )-Fliiche von Co(NH,),(SO,), . 6 H,O-Einkristallen wurde in Abhiingigkeit von der Ubersiittigung der wiirjrigen Losungen im Nullfeld und bei Magnetfluedichten von 7 T gemessen. Die Ergebnisse dieser und anderer Messungen zeigen, daI3 bei gegebenem auI3eren Feld in Gleichgewichtsnhhe keine me& bare Beeinflussung beobachtet wird (thermostatischer Feldeffekt). Dagegen treten deutliche Effekte bei extremen relativen Ubersiittigungen auf (kinetischer Feldeffekt).

Influence of a Static Magnetic Field on the ⟨100⟩ Growth Rates of Sodium Chlorate Crystals from Aqueous Solution

“…To determine whether the thermodynamic effect of the applied magnetic field can contribute to the increase of growth rates of the observed crystals, the temperature shift ΔT (the corresponding isothermal change of supersaturation) was estimated. The proposed formula was used, 3 =…”

“…To determine whether the thermodynamic effect of the applied magnetic field can contribute to the increase of growth rates of the observed crystals, the temperature shift Δ T (the corresponding isothermal change of supersaturation) was estimated. The proposed formula was used, normalΔ T = H 2 T 2 normalΔ 0 H μ 0 χ , where H is the strength of the magnetic field, T is the growth temperature, Δ 0 H is the molar enthalpy of crystallization, μ 0 is the magnetic permeability of the vacuum, and χ is the molar magnetic susceptibility of the solution. The estimated value of the temperature shift of the crystallization temperature caused by the magnetic field is Δ T ≈ 4.2 × 10 –4 .…”

“…On the other hand, the {110} face growth rates of diamagnetic Ni(NH 4 ) 2 (SO 4 ) 2 •6H 2 O, as well as {100} face growth rates of diamagnetic sodium chlorate crystals showed no changes during growth in a magnetic field, at supersaturation of 2 and 11%, respectively. 3 The growth rates of cadmium phosphate crystals nucleated and grown at different supersaturations were higher for crystals grown in a magnetic field of 0.27 T, than for crystals growing in zero field. 4 The displacement rate of the (100) faces of ammonium dihydrogen phosphate crystals was lower when a magnetic field of 0.17 T was applied.…”

“…The same authors showed that the (110) face growth rate of paramagnetic Co(NH 4 ) 2 (SO 4 ) 2 •6H 2 O, parallel to the magnetic field up to 7 T, exhibits a small increase. 3 This effect increased with increasing supersaturation of the solution. On the other hand, the {110} face growth rates of diamagnetic Ni(NH 4 ) 2 (SO 4 ) 2 •6H 2 O, as well as {100} face growth rates of diamagnetic sodium chlorate crystals showed no changes during growth in a magnetic field, at supersaturation of 2 and 11%, respectively.…”

“…The growth rates of paramagnetic Ni­(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O crystals increased slightly at high values of solution supersaturation. The same authors showed that the (110) face growth rate of paramagnetic Co­(NH 4 ) 2 (SO 4 ) 2 ·6H 2 O, parallel to the magnetic field up to 7 T, exhibits a small increase . This effect increased with increasing supersaturation of the solution.…”