Beckman DU spectrophotometer, about 1950
The DU spectrophotometer measures the amount of ultraviolet light absorbed by a substance. Developed by Arnold Beckman at National Technical Laboratories to measure the amount of vitamin A in food, it came to be widely used to identify and measure a variety of substances. The DU spectrophotometer was one of several revolutionary devices invented by Beckman: the first "black boxes" in the chemical laboratory. It revolutionized laboratory work by replacing labor-intensive and bulky (and openly visible) chemical procedures with a simple, boxed electronic instrument in which only input and output could be seen.
DeWitt Stetten, Jr., Museum of Medical Research, National Institutes of Health