695 



it was found that in layers of 20 cm., a solution of 0,41 percentages 

 hj weight sliowed a pronounced absorption-band in the yellow and 

 blue part of the spectrum between the wavelengths of 5510 and 

 6520 A.U. For concentrations of 0,827,, and r/„ Jio light was 

 transmitted; but the solution just mentioned allowed the light to 

 come through between 4850 and 5515 A.U. With a solution of 0.3 1'/o 

 these limits were: 4770 lo 5670 A.Ü., and 6480 A.U.; with 

 one of 0.277,,: 4720 to 5750, and 6450 A.U.; etc. Determinations 

 corresponding to wave-lengths within these limits can only be made 

 with extremely diluted solutions, and the incertitude of the readings 

 caused thereby may explain the deviations of the values obtained 

 in the case of the laevo-, and dextrogjratory components, in so far 

 as these values are observed in the immediate vicinity of the deep 

 minimum in the dispersion-curve. But notwithstanding this incerti- 

 tude, the charactei-istic slope of the dispersion-curve is in all cases 

 fixed with full certainty. 



For the salt from the tirst fractions, we found values of the 

 rotation in good agreement with each other, which are suited to 

 elucidate the strange form of the dispersion-curve (tig. 1) immediately : 





4000° 

 SOOO' 



/.'avc-u/i/A , 



MOO WO <t900 SOOO 5100 5Z00 5300 5^00 5500 5600 S700 5SQ0 5900 MOO MOO 6700 WOO 6'tOO - 7000 dnas/rrrri - 7//lltv . 



Fig. 1 . Molecular Rotatory Dispersion of Laevogyrutory 

 Potussimn Cobalti-Oxalate (-\- 1 H..0). 



