Which rule states that the entropy of fusion is a constant ==

Which rule states that the entropy of fusion is a constant == Richards rule states that the entropy of fusion is a constant for most metals. Fermat’s rule helped in finding the greatest and smallest ordinates in curved lines and Charles law states that pressure remaining constant, the volume of a given mass of gas increases or decreases by 1/273 part of its volume at 0 degree Celsius for each degree Celsius rise or fall of its temperature.