ABSOEPTION SPECTKA OF SOLUTIONS. 



37 



lengths being absorbed by its solutions. The regions of the spectrum ibr which I give 

 Vierordt's observations are, therefore, on the red-ward side only of the absorption l)and. 



The first table gives observations on the three strongest solutions examined : 



If these results be plotted in the same way as above it will be found (1) that the curve 

 of the strongest solution is highest and that of the weakest solution lowest ; (2) that the 

 curve for the strongest solution at the point corresponding to wave length 497'8 is steeper 

 than the curve for the intermediate solution at the point corresponding to the same wave 

 length, and that the latter at the point corresponding to wave length 490'2 is steeper than 

 the curve for the weakest solution at the point corresponding to the same wave length ; 

 and consequently (3) that if the curves be produced beyond the limits of the experiments, 

 until they cut the line of zero intensity, in such a way as to maintain the general trend 

 which they have within the limits of the experiments, the curve for the strongest solution 

 will cut the line of zero intensity at a point nearer the red than the others, and the curve 

 for the weakest solution at a point farther from the red than the others. In other words, 

 the region of complete absorption seems to move somewhat towards the red with increase 

 of concentration, while the absorption in the penumbra diminishes. 



The next table gives the observations on the two weakest solutions examined : — 



If these results be represented graphically it will be found that the curves are not 

 quite so simply related as those of the stronger solutions. But between wave lengths 



