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. Encased in a metal container, the device occupied less counter space than conventional bench apparatus, and hid the procedures inside a box. A technician placed a specimen on a slide, inserted it into the instrument, and recorded the readings. Historians of science theorize that "black box" devices are basic to modern laboratory practice. A device and its output replace the hand, eye, and judgment of the scientist. The standardized inner workings and seemingly objective output of the black box can more easily evade or withstand legal scrutiny.