On January 12, 1785, French chemist and physicist Dulong was born. Dulong discovered nitrogen chloride at the age of 26 and produced strong nitrogen chloride two years later. At the age of 34, Dulong and Perty discovered that the product of the specific heat capacity and the atomic weight of most solid simple substances is almost equal. This is the famous Dulong-Perty law, which has played a very important role in the history of chemical development. role.