When measuring a melting point, it is important to heat the sample strongly near the melting point to ensure that the crystals melt quickly to keep a narrow melting point range.

pl help me

It is important to have uniform heating at the time of melting and heating should be fast initially but slow heating should be done at the time of melting.This will help in observing a narrow melting range also.

Thanks Uma that makes sense.

Experts,

I have an irrelevant question here. Do hard rocks melt or dissolve ?? If so, which chemical can be used ?? A hole of 100 cms to be made on a particular portion of huge rock.

 It is difficult to melt rocks.It will better if they can be dissolved using  strongs acids.

what type of acids ?? could you please suggest few strong acids... I have tried few like nitric acid and few others... but no use

Try other acids ...at least it can make it slightly porous which you can drill easily.