Determination of the Atomic Weight of Cadmium and the Preparation of Certain of Its Sub-CompoundsJones, Harry C. (Harry Clary)
Science
Determination of the Atomic Weight of Cadmium and the Preparation of Certain of Its Sub-Compounds
Jones, Harry C. (Harry Clary)
Atomic weights; Cadmium; Thesis (Ph. D.)
While the decomposition of Cd₄Cl₇ with water cannot at present be fully
explained, yet it is clear from the analyses that one eighth of the
total cadmium is thrown down as a white precipitate and a crystalline
compound which as will be seen passes over into cadmous hydroxide. One
half of the cadmous chloride is oxidized to cadmic chloride taking the
chlorine from the other half.
The compound Cd₄Cl₇ was treated directly with absolute alcohol with
the hope of obtaining the crystalline substance in an undecomposed
condition. Although a substance of the same general appearance as that
formed in the presence of water was obtained yet it decomposed so
readily that a satisfactory analysis could not be made.
Notwithstanding the rapidity with which the decomposition of the
crystalline compound begins, long continued washing was necessary in
order to completely remove the chlorine. The extraction of the last
traces of the halogen is hastened by the use of warm instead of cold
water. The temperature of the water must not exceed 50°C. In water
whose temperature approaches the boiling point the hydroxide is slowly
decomposed with liberation of metal.
The new hydroxide is a strong reducing agent. It dissolves in dilute
acids; yielding with nitric acid oxides of nitrogen, with hydrochloric
or sulphuric acid free hydrogen. After washing with warm water until
all the chlorine had disappeared, it was dried over phosphorus
pentoxide and analyzed.
First determination of cadmium.
Amount of substance used .0968 gr.
” ” cadmium found .08415 ”
Cadmium.
86.93 per cent.
Second determination of cadmium.
Amount of substance used .09806 gr.
” ” cadmium found .08522 ”
Cadmium.
86.91 per cent.
The calculated percentage of cadmium in Cd(OH) is:
Cadmium.
86.79 per cent.
The determination of water in cadmous hydroxide was made by placing a
small specimen tube containing the hydroxide in a Kjeldahl flask which
was heated in a bath of concentrated sulphuric acid. During the heating
a slow current of dry nitrogen was passed over the substance.
First determination of water.
Amount of substance used .08434 gr.
” ” water found .00609 ”
Water. 7.22 per cent.
Second determination of water.
Amount of substance used .08895 gr.
” ” water found .00600 ”
Water. 6.74 per cent.
Third determination of water.
Amount of substance used .11766 gr.
” ” water found .00856 ”
Water. 7.25 per cent.
Average amount of water = 7.07 per cent.
The calculated percentage of water in Cd(OH) is, 6.99.
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