Carbon crucibles/sample vessels

The extent of reaction varies depending on the location of the sample in the vessel. This is clearly seen in the following example of the thermal decomposition reaction of zinc hydroxide carbonate [4]. The reaction was carried out in a flowing air atmosphere using a hemispherical Pt/Ph crucible of 16 mm diameter x 8 mm, a heating rate of 0.5°Cmin , aimealed isother-mally at 185 C for 5 h. The reacted sample taken from various parts of sample vessel was analyzed by X-ray diffractometry. The amounts of ZnO in the sample were 50% in concentric zones, 70% at the surface layer and about 25% at the bottom zone. 

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