Chemical Constitution of Saline Solutions. 305 
CuBr,5H,0 is a finely crystallized salt with a greenish golden colour. With 
one-third of its weight of water it forms an intensely dark madder brown solution. 
The added water here corresponds to about four molecules if the anhydrous 
salt were used, or six molecules with the above crystallized hydrate. If the 
saturated solution be mixed with 14 to 14 volumes of water, it is changed to a 
grass-ereen liquid; a further addition of 1} volumes of water yields a blue solu- 
tion; and if the addition of water be continued until the liquid is increased to seven 
times that of the original solution, a blue colour indistinguishable from that of 
cupric sulphate is the result. 
The lustrous black anhydrous salt, CuBr, dissolves in water with the same 
brown colour, and undergoes the same colour changes upon dilution. It is 
remarkable to see the golden green crystals come out of the solution, which is 
almost black. There is also a remarkable similarity between the colour of the salt 
when partially dehydrated and that of the concentrated solution. 
This cupric bromide, CuBr,°5H,O (see p. 302), isa striking example of a 
peculiarly unstable condition which characterises the copper and nickel haloid 
compounds. The simple exposure of the crystals to ordinary undried air at or 
about 16° causes them to become of a very dark brown colour, almost black, and 
of the same colour as the solution ; and at the same time that they undergo this 
change in colour, they lose as much as 9 per cent. of water. In other words, 
they effloresce and become brown. In this condition, the compound undergoes 
deliquescence in moist air, forming a very dark brown solution. 
NiBr,°6H,0, rich emerald green crystals, behaves in the same manner as the 
cupric bromide; that is to say, it effloresces and becomes brown. A concentrated 
solution made by adding water to the amount of about one-third the weight of 
the salt is reddish brown. The amount of added water is from three to three and 
a-half molecules to one of salt. When two volumes of this solution are mixed with 
one and a-half volumes of water, the colour changes to a rich yellowish green; if 
made up to three times its original volume, the liquid is apple-green in colour. 
It is quite evident that at 16° and 20°, the most stable hydrates of the 
foregoing compounds are CuCl,’H,O, CuBr,"H,O, and NiBr,2H,0. 
Nickel Iodide, Nil,-9H,O, the bluish green crystals of the compounds behave 
like the cupric and nickel bromides. <A solution made from the crystals, with a 
minimum of water, is of a yellowish brown colour. 
The addition of 25 volumes of water converts it into a yellowish green liquid, 
which does not undergo any further alteration by dilution. 
Solutions in Alcohol. 
The yellow anhydrous cupric chloride, CuCl,, dissolves in alcohol with a 
brown colour. The dihydrated salt, CuCl,2H,O, dissolves in alcohol with 
TRANS. ROY, DUB. SOC., N.S., VOL. VII., PART VII. 2U 
