86 Dr. W. A. Miller on some Cases of Lines 



of the molecules of which, it is all but certain, is far more 

 complicated than such an apparent simplicity might warrant 

 us in expecting. 



In fig. 1 some of the principal solar lines are depicted as 

 fixed points of comparison. 



Fig. 2 gives the general appearance of the lines presented 

 by iodine ; the specific gravity of this vapour is 8'707 ; the 

 lines in this case are most distinct in the orange and yellow 

 portions, and in the green becoming so numerous as to obli- 

 terate it: these lines are not sharply defined, but shadow off 

 into the lighter spaces very gradually*. In the more refran- 

 gible part of the spectrum I did not discern them. 



Fig. 3. Bromine shows lines corresponding to those of 

 iodine; they are less distinct, however, and can scarcely be 

 discerned in the orange portions ; the violet end of the spec- 

 trum is entirely intercepted. Specific gravity 5*390. 



Fig. 4. Some of the principal lines in the peroxide of ni- 

 trogen, NO4, specific gravity 3*183, the gas is of a deep 

 orange : in this gas one vol. of nitrogen and two of oxygen are 

 condensed into one. 



Fig. 5 gives some of the groups exhibited by the peroxide 

 of chlorine, Clg Og ; these are principally confined to the blue 

 and indigo portions, the colour of the gas being a bright 

 orange. No correspondence between the position of the 

 principal groups in these two gases is observable. 



It appeared to me of great interest now to ascertain what 

 influence the successive steps of oxidation of the same body 

 might have upon the spectrum ; and two classes of substances 

 presented themselves as well-adapted to this inquiry, viz. the 

 oxides of chlorine and of nitrogen. 



Thanks to the researches of many eminent chemists, and 

 especially of Millon and Pelouze in the last few years, we 

 are now in possession of means for preparing and insulating 

 these compounds of chlorine in a state of purity. Finding the 

 lines (fig. 5) in the gas extricated from chlorate of potash on 

 the addition of sulphuric acid, I next prepared some pure 

 chlorous acid from chlorite of lead (PbO, CIO3); this salt, 

 on the addition of nitric acid, furnished chlorous acid (CIO3) 

 in a state of purity. In this gas 2 vols, of chlorine and 3 vols, 

 of oxygen are condensed into 3 vols., and it has a specific 

 gravity of 2*646 ; and on proceeding with prismatic analysis 

 of the transmitted light, the very same series of lines was pro- 



* I am informed by Prof. Miller, that with instruments of hi<;h magni- 

 fying power and accuracy of definition, these bands are seen distinctly to 

 be composed of very fine lines, increasing in number and strength towards 

 the central or darkest portion of the band. 



