EFFECT OF DILUTION ON ABSORPTION OF LIGHT. 19 



For B the concentrations used were 1.025, 0.01025, and 0.00205 normal. 

 The depths of layer were the same as used in A. It is seen that the dilu- 

 tions are just one-half those of the corresponding layers in A. 



The concentrations of solutions used in making C were just half of those 

 in B, i. e., 0.512, 0.00512, and 0.00102 normal. In the entire plate, as in 

 all the dilution work, the most dilute solution is always nearest the spark 

 spectrum. 



Since very much of the finer detail and several of the narrowest bands 

 are lost in reproducing and printing the films, our discussion is always based 

 upon the original photographic film. Lines will frequently be discussed 

 which do not appear on the printed plates, but which are very clear and dis- 

 tinct on the photographic film. 



A study of A shows complete absorption in the violet up to X3350, then 

 slight transmission for about 50 a.u. The faint hazy band X3400 and the 

 well-defined band X3450-X3600 are not affected by the change in dilution. 

 Hazy bands appear at X3820, X4040, and X4200. Their intensities do not 

 seem to be affected by dilution. The beautiful sharp band X4275 is slightly 

 more intense in the most concentrated solution. The effect of dilution, if 

 any, on the bands X4325, X4440, X4600, X4690, X4750, X4820 is not measur- 

 able. On the original film they appear slightly broader, but not more 

 intense, on the third strip. 



Bands which have their centers near X5100, X5200, and X5800 are decidedly 

 affected by dilution, the former two appearing distinctly as independent 

 bands in the most dilute solution, diffuse with a single broad band with the 

 center near X5150. There is the greatest change between the second and 

 third strips (in discussing any plate, strip 1 is always nearest the spark lines). 

 The broadening of these bands with increase in concentration, both of which 

 have rather hazy edges, is fairly uniform, i. e., they widen both towards the 

 red and violet ends of the spectrum. 



The intense band which extends from X5690 to X5850 is affected very 

 markedly by concentration, the widening being almost entirely towards the 

 red end of the spectrum. The violet edge is hardly affected, while the wid- 

 ening towards the red is about 50 a.u. Here also the change in the width of 

 the band is greatest where the change in concentration of the solution is 

 greatest. There is a very faint band, X6225, which appears slightly more 

 diffuse in the most concentrated solution. 



The concentrations of the solutions used in B are just one-half those of A, 

 and it is seen that some of the smaller bands are lost, while the broader ones 

 have split into two or more smaller bands. In this film, bands near X3425, 

 X3475, X3520, X3575, X4275, X4340, X4450, X4700, X4750,X4820,X5100,X5120, 

 show no change with dilution. The broad band X5700-X5825 shows a widen- 

 ing of about 25 a.u., being the only band which is changed by concentration. 



C of this plate is the spectrogram of solutions twice as dilute as those of B. 

 No band on this plate shows any appreciable change produced by dilution, 

 except probably a slight widening of X5750. 



