Is using melting/boiling point good to measure volatility?
According to this Wikipedia page:  


  In chemistry and physics, volatility is the tendency of a substance to
  vaporize. Volatility is directly related to a substance's vapor
  pressure. At a given temperature, a substance with higher vapor
  pressure vaporizes more readily than a substance with a lower vapor
  pressure.  


So, I'm not sure how much information on volatility you will get from melting point measurements.  Ideally, the enthalpy of vaporization would be the best measurement, but, if it fits your needs, the boiling point at ambient pressure is a simple way to determine whether there is a significant difference in the volatility of various compounds.