Spectra of certain Uranous and Uranyl Compounds. 569 



The general effect of the presence of free acid is to make 

 the uranyl bands narrower and much sharper. The bands of 

 uranyl nitrate in aqueous solution * are of shorter wave- 

 lengths than those of the other uranyl salts. The effect of 

 sufficient free nitric acid is to shift the b, c, d, e, and / bands 

 about 30 A. U. to the violet, and to make all the bands 

 much sharper. 



The absorption of a solution of uranyl nitrate with water of 

 crystallization in strong nitric acid consists of bands shifted 

 slightly to the violet, as compared with the absorption of anh\ - 

 drous uranyl nitrate in nitric acid. The former solution 

 when freshly prepared gave the fine band absorption spectra 

 of nitrogen dioxide. 



The addition of sulphuric acid to an aqueous solution of 

 uranyl sulphate causes the b. c, i,j, Jc, I, and m bands to be 

 shifted towards the red, thee? and h bands to come together, 

 while the remaining uranyl bands are apparently shifted to 

 the violet ; the d band doubling. 



Free acetic acid has very little effect on the position of 

 the uranyl acetate bands. The effect of free hydrochloric 

 acid on uranyl chloride is to shove the uranyl chloride bands 

 into the red, and also to change very greatly the relative 

 intensities of these bands. 



The study of the effect of the presence of foreign salts lias 

 been limited almost entirely to the chlorides. Strontium, 

 zinc, calcium, and aluminium chlorides cause the uranyl and 

 uranous bands of aqueous solutions to appear much stronger; 

 and in general the presence of these foreign salts causes the 

 bands to be shifted to the red. This shift is a gradual one, 

 being greater the more foreign salt present. In the case of 

 the addition of aluminium chloride f to an aqueous solution 

 of uranyl chloride the e (\44G0) and /(A 4315) bands merge 

 into one broad band. 



The absorption of concentrated aqueous solutions of 

 mixtures of uranyl chloride with aluminium chloride, or zinc 

 chloride, or calcium chloride, or hydrochloric acid is practi- 

 cally identical, and it seems quite possible that the effect 

 upon the bands is due largely to the presence of the chlorine 

 ion. 



Very interesting changes in the uranous and uranyl bands 

 are caused by adding acids to solutions of uranium salts. 

 Acetic, hydrobromic, hydrochloric, nitric, and sulphuric 

 acids have been added to aqueous solutions of uranous 



* Phys. Rev. xxix. p. 555 (1009). 



f Amer. C'hom. Jo urn. xliii. p. 37 (1910). 



