[1][4] As a chemist and a scientist, Mitchell's work covered a wide range of topics.

[1][4] In 1907 he advocated using a pinhole camera to photograph the sun in an article in Knowledge and Scientific News, a method which he notes was known as early as 1615 but seemed to have been forgotten.

In 1915, he gave testimony about the invisible ink used in the case of German spy, Anton Kuepferle.

White opposed parts of the will that suggested the establishment of a hierarchy in the Baháʼí Faith.

[13] White placed Mitchell's signed report on the writing shown on the photographs of the document with the U.S. Library of Congress in 1930.