Jack McDowell was born in 1925 and raised on a small farm near McMinniville, Tennessee. He obtained a BS in chemistry from Tennessee Technological University in 1951. His first employment was with Union Carbide Nuclear in Oak Ridge as an analytical chemist working on the separation of uranium from nitrate solution using dibutoxytetraethyleneglycol for gravimetric analysis and diethyl ether for colorimetric determinations.
He received a master’s degree in inorganic chemistry in 1954 from the University of Tennessee and joined the Materials Chemistry Division of the Atomic Energy Commission at the Oak Ridge National Laboratory (ORNL). At this time the primary objective of his team was to recover uranium from low grade ores. The use of kerosene solutions of alkylamines was developed into a successful process that as the ‘Amex’ process was used world-wide. At this time Jack also worked on fundamental studies of the chemistry of primary and secondary amines and their use in phase transfer systems. These studies were later extended to other extractant systems such as: bis(2-ethylhexyl)phosphoric acid (1962); various neo-carboxylic acids (1969); phosphine oxides, carbamoylmethylphosphonates, and a variety of neutral solvating extractants including crown ethers (1978). Jack and his colleagues provided the driving force for the first international solvent extraction conference in Gatlinburg, Tennessee in 1962.
When strategy in the USA turned away from nuclear fuel reprocessing this group were directed to ‘resource recovery’ or the use of solvent extraction hydrometallurgy to recover non-radioactive elements. Simultaneously, the group became increasingly interested in fundamental studies of solvent extraction systems, and the use of the technique to investigate the chemistry of the transplutonium elements. In this field Jack and colleagues studied the chemistry of nobelium using solvent extraction experiments on the isotope 255No (t½ 233 minutes) delivered in batches of 500 atoms from the Oak Ridge Isochronous Cyclotron. These experiments determined the valence (+2) and its ionic radius, reduction potential and complexing tendencies.
As noted above Jack McDowell worked extensively on crown ethers and was one of the first to develop practical systems using these extractants. In particular he developed synergistic combinations of crown ethers with organophilic extractants such as the sulfonic, phosphoric and carboxylic acids. These mixtures provided the first highly selective extraction systems for a number of alkali and alkaline earth elements including cesium (1988-90).
Problems with the accurate determination of low concentrations of α-emitting nuclides with existing instrumentation led to the development of a liquid scintillation alpha counting and high resolution spectrometric method that allowed accurate determination of very low concentrations even in the presence of a high beta/gamma background. This resulted in the production of a prototype instrument at ORNL in 1968, later commercialised as the Photon/Electron-Rejecting Alpha Liquid Scintillation (PERALS) spectrometer which was selected for the IR-100 Award in 1981 to Jack McDowell and G N Case. The use of this spectrometer with extractive scintillators is now called the PERALS method of alpha spectrometry. Following retirement from ORNL in 1989 Jack established a company, ETRAC Inc., to manufacture selective extractive scintillators for the PERALS method.
In Jack McDowell’s career he published more than 120 peer-reviewed publications, over 100 oral presentations, 6 patents and contributed to several books. He published one book, Liquid Scintillation and Alpha Spectrometry, and was co-author with his wife of an expanded and up-dated version of a book with the same title published by CRC Press.
He died in 1994.