Presented to the Board of University Studies of the Johns Hopkins
University for the Degree of Doctor of Philosophy.
by
John E. Bucher.
1894
Contents.
I. Introduction and Historical Statement 1
II. The Oxalate Method 3
Preparation of Pure Cadmium 3
Preparation of Nitric Acid 4
Purification of Water 4
Purification of Oxalic Acid 5
Preparation of Cadmium Oxalate 7
Procedure 8
Results 13
III. The Sulphide Method 16
Preparation of Hydrogen Sulphide 16
Preparation of Nitrogen 17
Mode of Procedure 18
Results 24
Discussion of the Results 24
Discussion of the Method 26
IV. The Chloride Method 33
Preparation of Cadmium Chloride 35
The Filters 48
Analytical Process 52
Results 57
Discussion of the Results 58
V. The Bromide Method 69
Preparation of Cadmium Bromide and Hydrobromic Acid 70
Method of Analysis 78
Results 80
Discussion of the Results 80
VI. Syntheses of Cadmium Sulphate 82
Results 90
Discussion of the Results 91
VII. The Oxide Method 94
Results 96
Discussion of the Results 97
Determination of Error 104
Discussion of the Oxalate Method 114
VIII. Other Methods 119
IX. Conclusion 122
Acknowledgement.
The author wishes to acknowledge his indebtedness for advice and
instruction to Professor Morse at whose suggestion and under whose
guidance this work has been carried on. He also wishes to express his
thanks for instruction to Professor Remsen in Chemistry, Professor
Williams in Mineralogy, Dr. Ames in Physics and Mr. Hulburt in
Mathematics.
Introduction and Historical Statement.
The atomic weight of cadmium has been investigated by a number of
chemists but the results obtained vary between wide limits. The work
described in this paper was undertaken with the object of finding the
cause of the discrepancy in some of the methods employed. A complete
historical statement has been given by Morse and Jones, (Amer. Chem.
Jour., 14. 261.) and it is only necessary, here, to give a summary for
the purpose of reference:
Ratio. At. Wt. Cd.
1818, Stromeyer, Cd : CdO 111.483
(Schweiggers Jour. 22, 336.)
1857, Von Hauer, CdSO_{4} : CdS 111.935
(Jour. f. Prakt. Chemie 72, 338.)
1859, Dumas, 1st series. CdCl_{2} : Ag 112.416
2d „ CdCl_{2} : Ag 112.007
(Ann. Chim. Phys. [3], 55, 158.)
1860, Lenssen, CdC_{2}O_{4} : CdO 112.043
(Jour. f. Prakt. Chem. 79, 281)
1882, Huntington and Cooke, CdBr_{2} : AgBr 112.239
„ „ CdBr_{2} : Ag 112.245
(Proceedings Amer. Acad. 17, 28)
1890, Partridge, 1st Series CdC_{2}O_{4} : CdO 111.816
„ 2d „ CdSO_{4} : CdS 111.727
„ 3d „ CdC_{2}O_{4} : CdS 111.616
(Amer. Jour. Sci.[3], 40, 377)
1892, Morse and Jones, 1st Method, Cd : CdO 112.0766
2d „ CdC_{2}O_{4} : CdO 112.632
1892, Torimer and Smithy CdO : Cd 112.055
(Zeit. f. Anorg. Chem. I. 364)
In this summary as well as in the rest of this paper the following
atomic weights are used:
Oxygen = 16.00
Sulphur = 32.059
Carbon = 12.003
Chlorine = 35.45
Bromine = 79.95
Silver = 107.93