page_title: DU spectrophotometer
section_title: Model DU
hierarchical_section_title: DU spectrophotometer / Development / Model DU
caption_attribution_description: Original photograph used for Figure 7. View of spectrophotometer showing disassembled absorption cell and photo-tube compartment from from Cary, H. H.; Beckman, Arnold O. (1941). "A Quartz Photoelectric Spectrophotometer". Journal of the Optical Society of America. 31 (11): p. 687. doi:10.1364/JOSA.31.000682. No copyright renewal for the journal (first renewal appears for 1951). No copyright renewal for the paper. No copyright renewal for the photograph (checked 1968, 1969).
context_page_description: The DU spectrophotometer or Beckman DU, introduced in 1941, was the first commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by a substance. This model of spectrophotometer enabled scientists to easily examine and identify a given substance based on its absorption spectrum, the pattern of light absorbed at different wavelengths. Arnold O. Beckman's National Technical Laboratories developed three in-house prototype models and one limited distribution model before moving to full commercial production with the DU. Approximately 30,000 DU spectrophotometers were manufactured and sold between 1941 and 1976.
  Sometimes referred to as a UV–Vis spectrophotometer because it measured both the ultraviolet and visible spectra, the DU spectrophotometer is credited as being a truly revolutionary technology. It yielded more accurate results than previous methods for determining the chemical composition of a complex substance, and substantially reduced the time needed for an accurate analysis from weeks or hours to minutes.
context_section_description: When RCA could not meet Beckman's demand for experimental phototubes, National Technical Laboratories again had to design its own components in-house. They developed a pair of phototubes, sensitive to the red and blue areas of the spectrum, capable of amplifying the signals they received. With the incorporation of Beckman's UV-sensitive phototubes, the Model D became the Model DU UV–Vis spectrophotometer. Its designation as a "UV–Vis" spectrophotometer indicates its ability to measure light in both the visible and ultraviolet spectra.
  The DU was the first commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by a substance.  As he had done with the pH meter, Beckman had replaced an array of complicated equipment with a single, easy-to-use instrument. One of the first fully integrated instruments or "black boxes" used in modern chemical laboratories, it sold for $723 in 1941.
  It is generally assumed that the "DU" in the name was a combination of "D" for the Model D on which it was based, and "U" for the ultraviolet spectrum. However, it has been suggested that "DU" may also reference Beckman's fraternity at the University of Illinois, Delta Upsilon, whose members were called "DU"s.
  A publication in the scholarly literature compared the optical quality of the DU to the Cary 14 Spectrophotometer, another leading UV–Vis spectrophotometer of the time.
caption: Disassembled absorption cell and photo-tube compartment, Cary & Beckman, 1941[26]:687
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