CHAPTER IV. 



INVESTIGATION WITH A QUARTZ PRISM. 



(Figs. 6, 7, and 8 ; Table IV'). 



As is well known, a quartz prism is the most useful in exploring the 

 spectrum from o.8 to 2.8 (x, where it becomes opaque. 



In the introduction, the work of Puccianti, who explored a number 

 of benzene derivatives up to 2.75 fi, has been noticed. His curves show 

 that all compounds, the molecules of which contain carbon directly 

 combined with hydrogen, present a maximum absorption at 1.71 /x, 

 while all the benzene derivatives have two other maxima in common 

 at 2.18 fi and 2.49 fi. The three alcohols examined have a band in com- 

 mon at 2.05/1. He examined 16 compounds, viz, carbon-tetrachloride, 

 carbon disulphide, methyl, ethyl, and allyl alcohol, ethyl ether, methyl 

 and ethyl iodide, ethyl benzene, ortho-, meta-, and para-xylene, toluene, 

 benzene, pyridine, and water. 



The results obtained by Puccianti seemed so unusual that a continu- 

 ation of the work was deemed necessary. Accordingly, 18 new com- 

 pounds were examined, also benzene to serve as a comparison with his 

 work. The new compounds are 1-pinene, benzaldehyde, chloroform, 

 thiophene, phenyl mustard oil, methyl salicylate, eucalyptol, caproic and 

 oleic acid, ethyl carbonate, methyl acetate, ethyl succinate, glycerin, 

 methyl cyanide, allyl sulphide, nitro-methane, eugenol, and safrol. Their 

 transmission curves are given in figs. 6, 7, and 8. Of the marked ben- 

 zene maxima those at 2.18 /x and 2.49/* agree with the values found by 

 Puccianti. The band found by him at 1.71 /a was located at 1.68 )n to 

 1.69 /A, which agrees with Donath.\ As a whole, the maxima of the 

 curves are in agreement. His curves show an oscillation of the maxi- 

 mum about the value 1.71 /x, just as will be noticed in the present curves. 

 The depression in the benzene curve at 1.02 fx is of interest, since the 

 photographs obtained by Abney and Festing^ show lines in this region. . 



It will be unnecessary to go into details in describing the absorption 

 spectra given here, and it will simplify matters to discuss the conspicu- 

 ous maxima. 



The hand at 0.84 /x. — In this region the dispersion of quartz is only 

 slightly less than at J.7 fx, while it is comparable with that of rock salt 



'Table IV is given at the end of the text. 

 ^Donath, loc. cit. ^Abney & Festing, loc. cit. 



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