Chemical Constitution of Saline Solutions. 217 
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 difference between oxygen-gas light and the sun-rays as a source of 
illumination. 
When 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 usual. This same solution was 
placed in a thick wedge-cell in order to measure this absorption band. It must be 
remarked that the solubility of the sulphate is less than that of the haloid salts of 
cobalt. 
A 
At 16° C. . Spectrum begins at : : 673 
Absorption Band, : : : : . 844 to 464 
Spectrum ends at : : 0 : 407 
At 100° C. . Spectrum begins at : A : : 685 
Absorption Band, . : ; . 613 to 649 
Spectrum ends at . : ; ; 406 
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(NO),.—Aqueous solution. Thick wedge. Gas-light. (Plate 
XXI.) 
Xr 
At 16°C. . Spectrum begins at : : : : ; 724 
Absorption Band, ! : . 491 to 479 
Spectrum ends at : : : : 416 
At 100° C. . Spectrum begins at : ; : 696 
Absorption Band, ; . 491 to 479 
Spectrum ends at ; ; ; 416 
Smalt glass of a deep blue tint. ‘Two thicknesses. 
Spectrum begins at ‘ : : : 5 718 
First Absorption Band, : : : . 665 to 581 
Second 55 a ; . 549 to 513 
Spectrum ends at : : , : 400 
A rise of temperature has no effect on these measurements, though the glass be 
heated by a Bunsen burner until near the 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. 
TRANS. ROY. DUB. SOC., N.S. VOL. VII., PART VIII, 2Q 
