Elmer Howard Loomis was born on May 24, 1861 in Vermillion, Oswego County, New York, United States, the son of Hiram Warren and Adaline Sabra (Sayles) Loomis. He was a descendant of Joseph Loomis of Braintree, Essex, England, who came to Massachusetts in 1638 and later settled in Windsor, Connecticut. Hiram Loomis was engaged in the insurance business, and was at one time a member of the New York legislature. He removed to Mexico, Oswego County, while Elmer was still young.
Loomis was educated at the academy in Mexico, Oswego County. In 1883 he graduated from Madison University (now Colgate). In 1890 he went to Germany for further studies. He began his studies at the University of Göttingen and later transferred to the University of Strassburg, where he received, in 1893, the degree of Doctor of Philosophy. His dissertation, "Ueber ein exacteres Verfahren bei der Bestimmung von Gefrierpunktserniedrigungen", was honored with a summa cum laude.
Loomis was a teacher of physics and chemistry for seven years in Colgate Academy, Hamilton, New York. In 1894 he became instructor in physics at Princeton University, and was later assistant professor and professor. He continued for some years to publish papers on the same general subject as that of his dissertation, on the freezing points of solutions, in which he presented a great collection of measurements that were carried to the highest degree of exactitude which the nature of the problem permitted. In particular he proved that non-electrolytes in solution obey Raoult's law with great precision, and he made what may be considered a final determination of Raoult's constant. These papers appeared in the Annalen der Physik and the Physical Review (1896 - 1901).
In 1929 he retired from his professorship. He was a man of strong philanthropic instincts, serving for years as a member of the Princeton board of health, and as a director of the New Jersey Sanitarium for Tuberculosis.
Loomis was a fellow of the American Association for the Advancement of Science and of the American Physical Society.
On July 23, 1885, Loomis married Mary E. Bennett of Mexico. By this marriage he had two children who died in infancy, and a son, who survived him. In 1904 his wife died, and on October 12, 1911, he married Grace Eaton Woods of Rochester, New York.
