82 ABSORPTION SPECTRA OF SOLUTIONS. 



the fourth strip the intensity of its violet edge has decreased while that of 

 the red edge has increased considerably, giving it the appearance of an 

 unsymmetrical band, with the maximum intensity towards the red. In the 

 fifth strip the violet shading from X 4280 to about A 4284 has disappeared, 

 leaving a band very nearly symmetrical about A 4290. It appears, there- 

 fore, that we are really dealing with two unresolved bands, one having its 

 center at about A 4285 and the other at X 4292. 



The band at A 4275, due to the aqueous solution, decreases in intensity 

 throughout, but more rapidly from the third to the sixth strips than at 

 first. Its position remains the same throughout. As near as the eye can 

 judge this band has had its intensity reduced to about half value, when 

 the fourth strip is reached, corresponding to 8 per cent of water in the 

 solution. The alcohol band at A 4292 also has about 50 per cent of its final 

 intensity in the same solution. 



The band at X 4760 shows the same kind of a change that we described 

 in some detail above, only here the change is much more gradual and easy 

 to follow. It also shows about equal intensity for the two sets of bands 

 when the amount of water is 8 per cent of the whole. 



The green and yellow bands are not sufficiently resolved in A to allow 

 the change in the individual bands to be followed, and hence these ap- 

 parently show only a gradual shift towards the red with decrease in the 

 amount of water. In B, however, they are both sufficiently resolved to 

 enable us to follow the change in each individual band, which, although 

 a little difficult on account of their large number and the incompleteness 

 of their separation, in some cases may still be done. The change is in 

 every respect the same as we have found for the other bands, namely, 

 those due to the aqueous solution diminish in intensity, and reach about 

 half value in the 8 per cent water solution, while those belonging to the 

 alcoholic solution increase in intensity as the amount of water is decreased. 



The band in the red near A 6800 shows the change very well indeed, 

 the "water" band having the position A 6800, while that pertaining to the 

 alcoholic solution is situated at A 6860, and hence the two are well sepa- 

 rated. Here the point of equal intensity appears to be reached in the 

 solution containing 10.6 per cent of water, but this is due to the fact that 

 the alcoholic band has a considerably greater intensity than that due to 

 the aqueous solution, conditions as to concentration and depth of layer 

 being the same. Taking this into account, it is seen that this band obeys 

 substantially the same rule as the others. 



The change in the band at A 7325 is more difficult to follow on account 

 of the small intensity of the photographic action on the less refrangible side 

 of this position. The band belonging to the aqueous solution may be seen 

 very clearly, even in the strip corresponding to the 2.6 per cent water solution, 

 but is, of course, entirely absent in the alcoholic solution. Its intensity in 

 the 2 per cent solution, however, seems a little greater than we should expect 

 from the behavior of the other bands, but this is perhaps due to the rather 

 weak photographic action in this part of the spectrum, combined with the 

 great intrinsic intensity of the band. The alcoholic solution transmits light 

 as far as A 7355, where its spectrum ends abruptly in a band. 



