Chemical Constitution of Saline Solutions. 275 



At 16°, measurements were made at the red end, X 670, and the blue end 

 X.425. 



At 70°, measurements as before at \ 557 and \ 431. Tliere was nothing 

 remarkable in this spectrum beyond the much greater intensity of absorption 

 at the higher temperature. 



Another solution prepared in the same way as the preceding, but which had 

 been kept some time and was of a dark greenish tint, was examined. 



At 16°, measurements were made at X 592 and X 557. 



At 70°, the only measurement possible was of transmitted rays at X 565. The 

 dark green tinge became indigo-blue. 



Cobalt Bromide, anhydrous, CoBrj. — This was dissolved in absolute alcohol. 

 Thin wedge. 



At 20°, the only measurements possible were made at X 585 and X 423. 



At 70°, at X 583-8 and X 433. An indigo-blue liquid unaltered by heating. It 

 is quite evident tliat the blue cobalt bromide in the hydrated state, CoBr2'6H20, 

 is contained in the alcoholic solution of the crystals, and that by heating the 

 solution to 70° it is rendered anhydrous. 



Cobalt Sulphoajanate, Co(CNS)2. — An aqueous solution of a purplish blue 

 colour, very dai'k. Thin wedge, sunlight. 



At 20°, measurements were made at X 724 and X 711. Spectrum terminates at 

 X432. 



At 100°, the solution was quite opaque at this temperature. 



Cobalt Iodide, CoL '61120. — A cold aqueous saturated solution of the brown 

 hexagonal crystals. The solution is brown at 16°; below this temperature some 

 of the substance crystallizes out, and the liquid becomes red. 



The solid salt dissolved in about one-sixth of its weight of water, correspond- 

 ing to four molecules of water to one of salt, or 16"227grs. dissolved in 2*675 grs. 

 of water at 16°, forming one of the densest saline solutions known; its specific 

 gravity at 21° C. being 2-0817. Thin wedge, gas-light. 



At 20°, a very little light, transmitted at X 627 and 536. 



At 50°, a little light transmitted at X 588. 



On mixing with water, a red solution is formed. Thin wedge, gas-light. 



From 20° to 40°, the rays were transmitted from X 565 to 557. 



At 100°, the rays transmitted were from X 563 to 560. The red solution is so 

 diluted that heating to 100° is almost without effect upon it. 



Cobalt Iodide. Green dihydrate, Col3-2H20. — A cold saturated aqueous 

 solu<^^ion is of a very dark brownish green tint. Dilution with water, or 

 absorption of moisture turns it red and of a much lighter shade. 



At 20°, a very little light transmitted at X 588. 



