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An examination of some methods employed in determining the atomic weight of Cadmium cover

An examination of some methods employed in determining the atomic weight of Cadmium

Chapter 3: Introduction and Historical Statement.
By John Emery Bucher
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Science - Chemistry/Biochemistry

About This Book

A systematic laboratory study compares multiple analytical procedures for determining the atomic weight of cadmium. The author presents detailed preparation and purification of cadmium and reagents, then applies and evaluates gravimetric and synthesis-based techniques involving oxalate, sulphide, chloride, bromide, sulfate, and oxide preparations. Each section gives stepwise experimental protocols, filtration and drying practices, quantitative results, error analysis, and discussion of methodological limitations and reproducibility. The concluding discussion synthesizes discrepancies among methods and offers recommendations to reduce systematic error and improve consistency in future determinations.

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, CdSO4 : CdS 111.935
(Jour. f. Prakt. Chemie 72, 338.)
1859, Dumas, 1st series. CdCl2 : Ag 112.416
  2d „ CdCl2 : Ag 112.007
(Ann. Chim. Phys. [3], 55, 158.)
1860, Lenssen, CdC2O4 : CdO 112.043
(Jour. f. Prakt. Chem. 79, 281)
1882, Huntington and Cooke, CdBr2 : AgBr 112.239
  „ „ CdBr2 : Ag 112.245
(Proceedings Amer. Acad. 17, 28)
1890, Partridge, 1st Series CdC2O4 : CdO 111.816
  „ 2d „ CdSO4 : CdS 111.727
  „ 3d „ CdC2O4 : CdS 111.616
(Amer. Jour. Sci.[3], 40, 377)
1892, Morse and Jones, 1st Method, Cd : CdO 112.0766
  2d „ CdC2O4 : 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