266 



§ 2. A solution of the active components containing 3,797o of 

 the aniiydroiis salt, exhibits in a layer of 10 cm. an absorption- 

 spectrum, in which all violet, blue, and green rays are lacking, 

 while of the yellow light only a small portion is transmitted. With 

 increasing dilution a small extension of the spectrum is stated ; 

 more particularly the yellow and green rays are gradually better 

 transmitted and become more and more visible. In the case of a 

 solution of 0,5"^ even some greenish-blue rays were visible. In a 

 layer of 20 cm., the limits between which the light was not appre- 

 ciably absorbed, appeared to be about as follows : 



These data may give an approximate impression of the extension 

 of the light-transmission for several wave-lengths. In the red part of 

 the spectrum, the limit is situated at about 7700 A.U. ; however it 

 could not be fixed any more, because of the micrometer-screw of 

 the monochromator not going so far. 



By the study of the seven solutions just mentioned, the rotation 

 for any of these wave-lengths was measured in a way analogous to 

 that previously described ^). The total behaviour of these orange-red 

 to orange-yellow coloured solutions is most remarkable. For instance, 

 if only sufficiently concentrated solutions of the ^'/(/A^handed salt be 

 investigated (e.g. of lOVo), and thus only a limited spectral region 

 be taken into account, the observer would readily come to the con- 

 clusion, that his salt is /r7e?;ogyratory. The following data, obtained 

 within several spectral regions, by means of the seven solutions 

 mentioned, and which appeared, after controlling, to be sufficiently 

 exact, may elucidate this strange behaviour ^) with the simultaneous 



') F. M. Jaeger, Proceed. Kon. Acad. Amsterdam 17. 1227 (1915). 

 2) A. Werner, loc. cit. 1955. 



