8 INFRA-RED ABSORPTION SPECTRA. 



pounds like gypsum, CaSo3 + 2H20, has the same maxima at 1.5 /x and 

 2.0 /x as those found in pure water. It is unfortunate that he did not 

 compare the 2.95 /x band of muscovite (which has the H and O chemi- 

 cally combined) with pure water, since Paschen and Aschkinass dis- 

 agree on the exact location of this band. This disagreement will be 

 noticed in the present work. 



The most recent work in this line is that of Ikle,^ who used a fluorite 

 prism and a linear thermopile io'.5 wide. He investigated the relation 

 of absorption and thickness of the liquid used. He found no relation 

 between the refractive indices and dielectric constants, nor could he 

 detect a shift in the maxima for increase in molecular weight. Unfor- 

 tunately the thermopile used was wide, and for this reason the location 

 of the maxima is not very exact. 



OTHER INVESTIGATIONS. 



Kundt- investigated a series of solutions showing anomalous disper- 

 sion. He observed that, in different colorless solvents, the absorption 

 band of the solute is shifted toward the longer wave-lengths with in- 

 crease in the refractive and dispersive pozver of the solvent. H. W. 

 Yogel^ found that this is not true, but that the shift occurs in both 

 directions. A spectrophotometric study of indophenols by Camichel 

 and Bayrac* also shows that Kundt's law of the influence of the solvent 

 on the position of the maxima of absorption bands does not hold, for 

 the shift was from red to violet in an ortho-phenol, while upon substi- 

 tuting a meta- in an indophenol the displacement was from red to violet 

 or vice versa. Since then numerous investigations^ have afforded verifi- 

 cation of the statement that the absorption bands shift in both directions. 



The most thorough and at the same time the most important investi- 

 gation of solutions, for the optical region, is that of G. Kruss,^ who 

 examined 64 different compounds dissolved in CS2, CHCI3, and 

 C0H3OH. He observed that by the introduction of a methyl (CH3), 

 etiiyf (C2H5), oxymethyl (OCH3), or carboxyl (COOH) group, or 

 bromine, etc., in the molecule of the solute, the maximum of the absorp- 



ilkle : Phys. Zeit., 5, p. 271, 1904. 



^Kundt : Pogg. Ann., 1871-1872, and Weid. Ann., 4, p. 34, 1878. 



^Vogel, H. W. : Bed. Monatsber., p. 409, 1878. 



*Camichel & Bayrac : Jour, de Phys., Ill, 11, p. 148, 1902. 



^G. Kruss : Zeitt. f. Phys. Chem., 2, p. 372, 1888 ; ibid., 18, p. 559, 1895. Schiiltze : 

 Ibid., 9, p. 109, 1892. Grebe : Ibid., 10, p. 673, 1892. G. Kruss : Ber. der Deutch. 

 Chem. Gesell, 22, p. 2065, 1889. Kriiss & Oecomonides : Ibid., 16, p. 2051, 1883; 

 18, p. 1426, 1885. Bernthsen & Goske : Ibid., 20, p. 924, 1887. Liebermann & 

 Kostanski : Ibid., 19, p. 2327, 1886. 



