Transmission Measurements with the Beckman Quartz Spectrophotometer

Abstract

The Beckman quartz photoelectric spectrophotometer, covering the wave-length range from about 200 to 1200 millimicrons is proving of great utility in spectral transmission and absorption measurements. Essential features of the instrument are described, including a constant-temperature inclosure (for samples) designed and constructed at the Bureau. Various instrumental characteristics are noted and possible errors discussed, particularly those that may be present in the measurement of polarizing samples. Wave-length calibrations are shown for two instruments. A detailed over-all check of the reliability of data obtained on the Beckman spectrophotometer by means of glass standards of spectral transmittance shows it to give results over the wave-length range from 390 to 750 mμ fully as reliable as those obtained with our other spectrophotometers, if various precautions are taken.