Chemical Constitution of Saline Solutions. 



277 



No dark lines were observed in the violet, these being part of the solar spectrum, 

 and doubtless the end of the visible spectrum fell short of that usually observed 

 owing to the diffei'ence between oxygen-gas light and the sun-rays as a source of 

 illumination. 



Wlien the liquid was hot, the dark shading of the absorption band became 

 capable of measurement, but only at the top of the cell where the layer of liquid 

 was thickest, instead of at the middle as was visual. Tliis same solution was 

 placed in a thick wedge-cell in order to measure this absoi'ption band. It must be 

 remarked that the solubility of the sulphate is less than that of the haloid salts of 

 cobalt. 



A 



The green rays were so shaded in the above spectrum as to appear of a dark 

 olive green colour fading into the blue. On heating, they became black. The 

 absorption thus became complete. 



Cobalt Nitrate, Co(^ 0)2. — Aqueous solution. Thick wedge. Gas-light. (Plate 

 XXI.) 



Smalt glass of a deep blue tint. Two thicknesses. 



Spectrum begins at 

 First Absorption Band, 

 Second „ ,, 



Spectrum ends at 



718 

 665 to 581 

 549 to 513 



400 



A rise of temperature has no effect on these measurements, though the glass be 

 heated by a Bunsen burner until near tlie temperature when it begins to soften. 



It is thus rendered perfectly clear that anhydrous substances do not undergo 

 any change in composition which is indicated by a change in their spectra on rise 

 of temperature. 



TKANS. KOr. BUB. SOC, N.t^. VOL. VII., PART VIII. 2 Q 



