Himik
Chemist
If it melts far above its melting point, i.e. 10C+ it is not the right compound. If it melts below its MP and the range is broad it is most likely impure compound. If your powder melts within 3 degrees C, it is usually considered pure. You can test the purity of compounds by mixing the sample that you know is pure with the sample in question, if the MP becomes broad and depressed you have 2 different compounds, in other words your powder is bunk.