Zone refining or Fractional crystallisation

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Zone refining or Fractional crystallisation:

Metals in high purity can be obtained in this method which is based on the difference in solubility in the liquid and solid states of the metal, and that of impurity, Ge,Si, and Ga used as semi-conductors are refined by this method. Gallium arsenide and indium antimonide used as semi-conductors are also refined by this method. In this method, a circular heater is fitted around a rod of impure metal and slowly moved over the rod. At the heated zone, the rod melts and as the heater moves, pure metals crystallises while the impurities drain away to the other part. The heater may have to be moved from one end to the other end of the rod more than once. 

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Siemens Ozoniser how Siemens Ozoniser work

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Siemens Ozoniser:  This Ozoniser consist of two co-axial glass tubes fused together at one end. The outer side of the outer glass tube and the inner side of the inner glass tube are finally coated with tin foils as shown in the figure given below.  (Siemens Ozoniser)->2                                                     (Siemens Ozoniser)->1 These tin foil are connected  to the induction coil for supply of silent electric discharge. Pure and dry oxygen gas is passed into the apparatus through annular space. The gas is then subjected to the action of silent electric discharge where oxygen gets converted into ozone. The ozonised oxygen then comes out  of the apparatus through the outlet of the Ozoniser. (Siemens Ozoniser)->2
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Rutile structure

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Rutile structure: The radius radio is in the range 0.73 to 0.41. in rutile (TiO²) each Ti⁴+ ion is octahedrally surrounded by six O²- ions whereas each other O²- ion is surrounded by only three Ti⁴+ ions arranged at the tree corners of a plane triangle. The Co-ordination number of Ti⁴+ and O²+ ions are 6 and 3, respectively. It is not exactly a close packed structure. Ti⁴+ ions in rutile may however, be considered as forming a sufficiently distorted body centred cubic lattice.           Example  compounds  having radius ratio below 0.41 are SiO² and BeF² but these are only a few. The Co-ordination number of Si⁴+ and Be²+ is four and that of O²- is two. However, these are appreciably co-valent.
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Paramagnetic substances

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Paramagnetic substances:   The substances which are weakly attracted by magnatic lines of force are called paramagnetic substances and this phenomenon is called paramagnetism. These substances possesses permanent magnetic dipoles due to the presence of unpaired electrons. These substances lose their magnetic behaviour in the absence of an external magnetic field i.e. their magnetic behaviour is temporary. Examples, many transition metals and their ions i.e. TiO², VO², CuO, FeSO⁴ etc.
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