Part 1

Transcriber’s Notes:

Underscores “” before and after a word or phrase indicate italics_ in the original text. Small capitals have been converted to SOLID capitals. Typographical and punctuation errors have been silently corrected. The symbol “ī” (small i with macron)was used in place of the numeral 1 (one) with macron. The symbol “̅2” (overline + 2) was used in place of numeral 2 with macron.

Determination of The Atomic Weight of Cadmium and The Preparation of Certain Of Its Sub-Compounds.

Dissertation,

Presented to The Board of University Studies of The Johns Hopkins University,

For The Degree of Doctor of Philosophy,

By Harry C. Jones

1892.

Contents.

Page Determination of the Atomic Weight of Cadmium 1 Introduction and Historical Statement 2 Preparation of Pure Cadmium 22 The Preparation of Pure Nitric Acid 28 The Arrangement of Crucibles 30 The Mode of Procedure 32 The Weighing 37 Taring the Crucibles 40 The Results 42 Objections to the Method 45 Advantages of the Method 48 The Oxalate Method 50 Preparation of Pure Oxalic Acid 51 Preparation of Cadmium Oxalate 52 Mode of Procedure 53 The Drying and Weighing of the Oxalate 55 The Results 58 Advantages of the Method 60 Disadvantages of the Method 61 Preparation of Certain Sub-compounds of Cadmium 63 Historical 64 The Preparation of Cd₄Cl₇ 66 The Preparation of Cd₄Br₇ 78 The Preparation of Cd₁₂I₂₃ 82 The Preparation of Cadmium Hydroxide and Oxide 82 Notes on Crystals of Metallic Cadmium 97 The Cohesion Phenomena of Cadmium 103 Biographical Sketch 106

Acknowledgment.

It affords me great pleasure to express my sincere thanks to Professor Remsen for his instruction and personal supervision during my entire connection with the University; to Dr. Morse, under whose immediate guidance the work described in this dissertation was completed; to Dr. Renouf for valuable assistance in qualitative chemistry and to Dr. Williams, with whom the branches of mineralogy and geology were followed as subordinate subjects.

Determination of the Atomic Weight of Cadmium.

Introduction and Historical statement.

A careful examination of the literature on the atomic weight of cadmium will convince any one that considerable uncertainty yet remains in reference to this constant. Six experimenters have worked on this problem but the results of no one of them can be accepted as being more accurate than those of all others. The value assigned to cadmium varies from 111.48 to 112.32 on the basis of oxygen = 16. The best work has apparently been done by von Hauer, Lenssen and Huntington. The results of these three seem entitled to about equal confidence, yet the figure obtained by von Hauer differs from that of Huntington by three tenths of a unit.

The more prominent difficulties which have been encountered were:

First. The preparation of cadmium compounds free from all impurities, and which at the same time were well adapted to weighing.

Second. The lack of a thoroughly simple and exact method for the analysis of cadmium compounds.

Third. Insufficient care in weighing in many cases whereby small errors were introduced into the results.

The methods which have been employed are:

1 Conversion of the metal into the oxide. (Stromeyer).

2 Conversion of the sulphate into the sulphide. (von Hauer and Partridge).

3 Decomposition of the oxalate to the oxide. (Lenssen and Partridge).

4 Determination of the chlorine in cadmium chloride, by which the relation between the chloride and metallic silver was established. (Dumas.)

5 Precipitation of the bromine in cadmium bromide as silver bromide. (Huntington.)

6 The conversion of the oxalate into the sulphide. (Partridge.)

The different pieces of work will be taken up in chronological order and briefly considered.

Stromeyer, Schurigg Journ. 22, 366. 1818, determined the atomic weight of cadmium a short time after the discovery of the element. He does not describe his method in detail but established the relation between cadmium and oxygen to be: