actinometern.

1833 Edinb. New Philos. Jrnl. 14 337 Mr Kämtz also made on a fine day..observations with an instrument invented by Sir J. Herschel, named Actinometer.

1858 Philos. Trans. (Royal Soc.) 148 499 The second actinometer, only arriving in Teneriffe at the conclusion of the summer, never got beyond the Consul's office in Santa Cruz.

1880 Contemp. Rev. Feb. 210 In interplanetary space, if the experiments with the actinometer are to be trusted, the temperature is not less than 256° Fahrenheit below the freezing point of fresh water.

1922 Jrnl. Ecol. 10 133 It is more difficult to make averages for the readings..owing to the great variations that occur..depending on whether the actinometer is placed where the sun reaches it directly or not.

1955 Jrnl. Animal Ecol. 24 326 The photometer reading was used as a simple measure of solar radiation, since its readings were shown to be proportional to the multi-directional total radiation (measured with a spherical actinometer).

1997 Brit. Jrnl. Hist. Sci. 30 340 The screen is removed again, the actinometer exposed to the sun for a minute, and the increase read off and recorded.

1866 J. W. Swan in Brit. Jrnl. Photogr. 16 Mar. 125/2 I name the instrument the ‘photographic Actinometer’, because it is exclusively designed for regulating the exposure in photographic printing.

1879 Photogr. in Cassell's Techn. Educator III. 326 The consequent progress of the printing may be most accurately determined by means of the actinometer.

1891 Internat. Ann. Anthonys Photogr. Bull. 347 On another day, the actinometer tint is obtained in five seconds.

1926 A. G. Tansley & T. F. Chipp Aims & Methods Study Vegetation 93 The ordinary photographic ‘actinometer’ or ‘exposure meter’ is a very useful instrument for roughly measuring the relative light intensities of different habitats.

1958 Newnes Compl. Amateur Photogr. vii. 94 Actinometers. Used for many years, but now obsolete, these measured the light intensity falling on the subject by the time taken by a printing-out paper to darken to match a standard tint.

2007 M. Osterman in M. R. Peres Focal Encycl. Photogr. (ed. 4) 75/1 The closest thing to an exposure meter in the 19th century was the actinometer.

1905 Proc. Royal Soc. 74 400 It has hitherto been supposed that an active mixture of hydrogen and chlorine, after standing in the dark for several hours, returned to its original inactive condition... By the employment of a quartz actinometer we have, however, succeeded in showing that no decay of activity takes place.

1929 Jrnl. Sci. Instruments 6 2 Szilard..prepared cadmium for the kathode of his photo-electric cell for use as an actinometer which was sensitive in the region 2950–3900 å.u.

1949 O. Warburg & V. Schoken in Arch. Biochem. 21 36 A chemical actinometer has been described, by which quantum intensities..can be measured manometrically.

1978 K. K. Rohatgi-Mukherjee Fund. Photochem. x. 301 Photodecomposition of K-ferrioxalate was developed into an actinometer by Parker and Hatchard.

2006 M. Montalti et al. Handbk. Photochem (ed. 3) xii. 601 In principle, any photoactive compound whose quantum yield is known could be used as an actinometer.