196 THE ROYAL SOCIETY OF CANADA 



DIVISION I 

 By Mr. V. P. Lubovich 



Part I. Infra Absorption of Aniline Dyes and Coloured 



Glasses 



(1) Introduction. 



Recent work by Meggers,' by Meggers and Kiess,^ and by 

 McLennan and Shaver^ shows that the photography of the spectrum 

 can be extended into the infra-red by using plates stained by certain 

 selected dyes. From the investigations cited above it is clear that to 

 get measurable results up to X 9000A exposures of from 20 to 30 

 minutes are quite sufficient, but beyond this limit it is possible to 

 photograph only with exposures ranging from 5 to 32 hours. 



According to investigations by Vogel* and Eder^ the maximum 

 of sensitivity of stained plates is always about 30 A on the red side 

 of the absorption maximum of the dye used. With this in mind a 

 research was undertaken on the absorption of the different dyes used 

 by the authors mentioned above, with the object of finding out 

 which dye could be used most successfully, for photograpiiy beyond 

 X 9000A. Owing to the small dispersion of prism spectrographs in 

 the infra-red, and also to the absence of well mapped standards 

 accurate measurements of photographed lines are possible only with 

 grating spectrographs. This fact makes it necessary to cut off high 

 order spectra by using filters. As experience has shown that it is not 

 always possible to rely on the data given by manufacturers of filters 

 the opportunity has been taken of coupling the investigation of the 

 dyes with the study of different filters, in the hope that the results 

 might prove useful in infra-red photography. 



(2) Method 



Owing to the fact that all staining baths contain a considerable 

 amount of ethyl alcohol and a very low percentage of dye, alcoholic 

 solutions of 1/10000 in four cases, and of 1/2000 in one case, were 

 investigated. As alcohol itself absorbs infra-red radiation in the 



^Meggers, Bull, of the Bureau of Standards, Vol. 14, 1917. 

 ^Meggers and Kiess, Bull, of the Bureau of Standards, No. 324. 

 ^McLennan and Shaver, Proc. Roy. Soc, A. Vol. 100 p. 200, 1921. 

 ^Vogel, Berichte, No. 6, p. 1302, 1873, No. 7, p. 976, 1874. 

 6Eder, Wien Berichte, 90 I, p. 1097 (1884), 92 II, p. 1346, 1885, 93 II, p. 4 

 (1886), 94 II, p. 75 and p. 378, 1886. 



