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when determining the melting point of an unknown substance it is common practice to fist determine...

when determining the melting point of an unknown substance it is common practice to fist determine rough melting point by quickly heating the sample followed by careful determination of melting point by gradually heating the sample at the rate of 1-2 C/min. What is the advantage of this two-step determination of the melting point?
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Answer #1

1) The first step is also known as approximate range analysis, in this step we just rapidly increase the heat by turning the knob and when the solid component starts meling we note the point that will provide us the approximate range possible.

Let this value be Tm

2) In the second step, accurately calculating the melting point, we start with the temperature that is let us say 20 degrees less than the value of Tm i.e. (Tm-20)C and then slow increase the temperature and check the solid for 1-2 min with the increase of 1-2 C/min to find the accurate melting point.

If we have done it directly by changing 1-2 C/min then it would have taken us a lot of time in doing and finding the correct meling point

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