Career
In 1944 he published a seminal work on countercurrent distribution, which became an important separation technique. Craig continued to develop the theory, improve the apparatus and devise new applications of the countercurrent distribution into the 1970s. Countercurrent distribution not only proved to be a useful separation technique, it also inspired the development of the field of countercurrent chromatography.
In 1950, Craig invented the rotary evaporator which is a necessary equipment in most chemical laboratories
He was elected to the National Academy of Sciences in 1950. He also was nominated for the Nobel Prize in Chemistry.