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THE DETERMINATION OF OZONE BY SPECTROBOLO- 

 METRTC MEASURE^IENTS 



By OLIVER R. WULF 



smithsonian institution and u. s. bureau of chemistry and soils 



(With Three Plates) 



In the fall of 1930, at the suggestion of Dr. C. G. xAbbot, measure- 

 ments of the transmission of visible light by ozone were made on the 

 solar spectrometer of the Smithsonian Institution at Table IMountain. 

 Calif. This determination of the absorption of ozone in the region 

 of its very weak absorption, practical in the laboratory only by the 

 method of photographic photometry, by which it has been done by 

 Colange/ can be accomplished by direct energy measurements on the 

 spectrobolometer because of its great sensitiveness and the extreme 

 intensity of the source. At the same time fluctuations in weather 

 conditions are likewise registered with great sensitiveness and consti- 

 tute a serious source of error in the measurements. But on the other 

 hand it is favorable that observations may be made of the absorption 

 of controlled amounts of ozone placed in the sun's beam with all other 

 conditions of operation identical with those of the regular solar 

 observations. One of the useful results of this work has been the 

 selecting of a large number of points on the solar hologram which may 

 be satisfactorily used for ozone determination. The present paper has 

 to do for the most part with the results of these measurements as 

 forming a basis for the determination of atmospheric ozone from 

 solar holograms and not with the results of their application. 



The essential apparatus used in this work auxiliary to the spec- 

 trometer is shown in Plate i. A cylindrical glass cell, 20.0 cm. long 

 and approximately 13 cm. in diameter, was mounted in the front 

 room of the spectrometer tunnel in such a way that it could be easily 

 moved in or out of the solar beam as it came from the coelostat mir- 

 rors on its way to the first slit of the instrument. The circular windows 

 of this cell were made of high-grade plane plate glass. These windows 



^ Colange, G., Journ. Phys. et le Rad., ser. 6, vol. 8, p. 254, 1927. 

 Smithsonian Miscellaneous Collections, Vol.85, No. 9 



