If the substance was a mixture of the two chlorides, when treated with water the cadmic chloride would most probably dissolve directly leaving the cadmous chloride to be acted upon by the water. The decomposition by water will however be seen not to be as simple as would be expected under these conditions.

From the above considerations it appears highly probable that the substance is a definite chemical compound of cadmic and cadmous chlorides. If cadmic chloride can form a chemical compound with the chloride of another element there appears to be no reason why it should not form a compound with another chloride of cadmium, as with cadmous chloride.

The preparation of Cd₄Br₇.

The anhydrous bromide of cadmium was prepared by dissolving the carbonate in an aqueous solution of hydrobromic acid, evaporating the bromide to dryness on the water bath and heating the residue in a current of dry hydrobromic acid gas. When the bromide was heated with an excess of the metal in an atmosphere of nitrogen it conducted itself in general like the chloride. When the molten bromide and the metal came in contact the salt quickly became deep red in color. After heating for some time considerable dissociation was produced by raising the temperature. This was more apparent in the preparation of the bromide than with the chloride. On cooling, the mass possessed a greenish tint which disappeared when cold, the bromide then being very nearly the same color as the corresponding chloride. Also like the chloride it appeared to be homogeneous and free from metal. Two determinations of cadmium and two of bromine were made, using the product as soon as prepared.

First determination of cadmium:

Amount ofsubstance used .3736  gr.
” ”cadmium found.16658 ”
Cadmium.
44.59 per cent.

Second determination of cadmium:

Amount ofsubstance used .35930 gr.
” ”cadmium found.16013 ”
Cadmium.
44.57 per cent.

First determination of bromine:

Amount ofsubstance used .66640 gr.
” ”bromine found.36953 ”
Bromine.
55.45 per cent.