Who invented Langelier Index?

The Langelier saturation index (sometimes Langelier stability index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pHs).
en.wikipedia.org/wiki/Hard_water