Open AccessA photoelectric spectrophotometer using dual electrostatic compensation
Publication year - 1934
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1934.0037
Subject(s) - monochromator , photometer , electrometer , photoelectric effect , optics , light source , physics , compensation (psychology) , integrating sphere , wavelength , psychology , psychoanalysis
The photometer here described is suitable for the purpose of measuring extinction coefficients of substances in solution, more particularly in the ultra-violet region. The method employed is a purely electrical one, and does not involve the use of any mechanical devices (sectors or wedges, etc.) for the quantitative variation of light intensity. Errors due to fluctuations of the light source are eliminated by the use of two photoelectric cells, while the simultaneous electrostatic compensation of both cells does away with the necessity of measuring or controlling times of exposure. The actual observations are of (i) a resistance plugged into a resistance box, and (ii) an electrometer defection. The former gives tbs approximate result and the latter the correction to be applied. II.Description of apparatus and method . The source of light is a vertical mercury vapour lamp, running at about 3½ amps, and about 100 volts terminal voltage. The light from this source is condensed upon the slit of a double quarts monochromator by a suitable cylindrical quarts lens with its axis vertical. means of the double quarts monochromator, which has auxiliary dispersing prisms rotated by means of wave-length drums, any desired wave-length emitted by the source can be selected and allowed to enter the photoelectric photometer.