1871.] Spectra of Metallic Compounds. 63 



spectra of the oxygen and haloid salts, and between the 

 haloid salts themselves, the differences are numerous and 

 striking. In addition to the lines in the less refrangible 

 portion of the spectrum, which are common to all, and 

 which belong to the metal as oxide, a great number of lines 

 in the green, blue, indigo, and violet are seen, whose form 

 and grouping are peculiar to the haloid salt under examina- 

 tion. In the spectrum of cupric chloride, the most noticeable 

 feature is the grouping of the lines, in the more refrangible 

 end of the spectrum, into pairs, in which the broader and 

 more conspicuous lines are separated by an interval of about 

 six degrees, while to their right, at a distance of about one 

 degree, another but much feebler line in each case is seen. 

 In the spectrum of cupric iodide no such symmetrical 

 arrangement is evident. With plumbic chloride the same 

 extension of the lines into the upper end of the spectrum 

 takes place. Many of the bands in the spectra of the 

 plumbic salts are beautifully shaded, and commence with a 

 feeble illumination on the side toward the less, and increase 

 to a line of maximum brightness on the side toward the 

 more, refrangible end of the spectrum, where they abruptly 

 terminate. 



Without detailing in this place what takes place when the 

 various metallic compounds are examined, it will be in- 

 teresting to note briefly the deportment of one of them — 

 cupric chloride. When a mass of this salt, which has not 

 previously been freed from water of crystallisation, is heated 

 on a platinum wire in the flame of a Bunsen burner, it 

 imparts in the first place a greenish illumination to a large 

 portion of the flame. On examining the flame through dark 

 blue glass, it is seen that the part immediately above the 

 heated substance is of a deep blue colour. This becomes 

 tinged with violet, and later a tongue of reddish flame rises 

 in the centre of the blue. If the substance be pushed into 

 the hotter part of the burner, this flame changes to a bright 

 white light, which at its upper edge becomes lurid again. 

 The spectrum in this case is continuous throughout the 

 middle and lower portion, the separate bands of violet still 

 remaining distinct. 



These phenomena are evidently of a mixed character. 

 When a mass of this salt is carefully heated, so that it is 

 slowly volatilised along with aqueous vapour at the outer 

 edge of the flame, a green band, extending from 6o*8 to 72*4, 

 alone makes its appearance. On heating a concentrated 

 solution of cupric chloride, the red lines from 37*8 — 44*8 

 appear synchronously with the green from 6o*8 to 72*4. It 



