92 



A STUDY OF THE ABSORPTION SPECTRA. 



solution of uranyl chloride and a 2.4 normal solution of aluminium (Plate 



49, B) were made. The depths of layer were 3, 6, 12, 24, and 35 mm. In 

 our discussion of the uranyl salts the effect of aluminium chloride was 

 described. The different effect of the aluminium chloride upon the a and b 

 bands is very marked. In the uranous solution the a band does not appear, 

 and in fact the bands here do not seem to coincide very well either in posi- 

 tion or intensity with the bands of uranyl chloride in water. The position 

 of the uranyl bands when aluminium chloride is added is: a, 4950; b, 

 4790; c, 4620; d, e, 4480-4420; /, 4270; g, 4135; h, 4010. 



(1) In uranyl chloride in aqueous solutions the addition of aluminium 

 chloride makes the uranyl bands much stronger. It causes the d and e 

 bands to come together to form practically one band. 



(2) In aqueous solutions of uranous chloride the addition of aluminium 

 chloride before the uranyl salt was produced causes the uranyl bands to 

 appear, the position of these bands being the same as in case 1. 



(3) The presence of aluminium chloride in both cases causes a greater 

 ultra-violet absorption. 



The effect of hydrochloric acid and zinc chloride on the uranyl bands 

 is very similar to that of aluminium chloride. 



Solutions of 0.2 normal concentration were made in very strong hydro- 

 chloric acid and zinc chloride solutions. These are represented by Plate 



50, A and B. The four spectrograms (Plates 49 and 50, A and B), were all 

 made under the same condition. Zinc chloride, hydrochloric acid, and 

 aluminium chloride have the common property of making the uranyl 

 bands much stronger. Hydrochloric acid and aluminium chloride increase 

 the ultra-violet absorption and cause the uranyl bands to shift much more 

 towards the red than zinc chloride does. The following table gives the 

 wave-lengths of the uranyl bands in aqueous solutions when the above 

 named substances are added: 



a. 



Pure U0 2 Cl a j 4920 



+ ZnCl 3 1 4930 



4-A1C1, 4950 



+ HC1 4950 



b. 



c. 



4740 4560 



4770 I 4600 



4790 4620 

 4800 I 4635 



4460 

 4400 



very! .... 

 widei 



44S0 4420 

 4480i 4420 



4315 4170 



4245 



4270 

 4280 



4025 



4115 



4135 

 4150 



4010 

 4015 



The bands of the aluminium chloride and hydrochloric acid solutions 

 do not coincide, and the relative displacements show very clearly when the 

 two original films are placed together so that the spark lines coincide. In 

 none of these spectrograms do the "characteristic " uranyl chloride bands 

 appear, probably on account of the large slit-width. 



The zinc chloride solution was made by dipping zinc in hydrochloric 

 acid of the same strength as was used to make the U0 2 C1 2 solution in 

 hydrochloric acid. To the zinc chloride and hydrochloric acid solutions a 

 normal solution of uranyl chloride was added so as to make the resulting 

 uranyl chloride solution 0.2 normal. 



