209 



together. In the table are therefore quoted those vahies which 

 approaclied nearest to the curve of the mean vahies. The dispersion- 

 cnrve sliows a tendency to gel more and more horizontal for wave- 



lengths beneath 5100 A.U. 



Rotation DISPERSION of dextrogyrate Potassium-Iridium-Oxalate 



(+ 1 H,0). 



Although the dispersion of these orange-coloured solutions is 

 extraordinarily strong, the slope of the curve is quite ditferent 

 from that found in the case of the corresponding rhodium-saU. This 

 fact proves the preponderant influence of the special nature of the 



14 



Proceedings Royal Acad. Amsterdam. Vol. XXI- 



