The distillation was carried out in hard glass tubes of the size of ordinary combustion tubing.

Fig. 1.

[Fig. 1.] represents such a tube. A hard glass tube, 600-700 mm. in length, was closed at one end and about 130 grams of cadmium introduced. The walls of the tube were heated and indented at the two points a, and b, with a red-hot file, dividing the tube into three sections marked A, B and C. The open end of the tube was drawn out, bent, and attached to a Sprengel air-pump by means of a rubber tube.

The joint was tied tightly with waxed cord and surrounded by mercury. When the manometer indicated that the tube was exhausted, it was gradually heated by the combustion furnace in which it rested. The metal in A melted and distilled slowly into the front portion of the tube. Most of it condensed in B, while a small part, together with any more volatile impurity, collected in C which was kept cooler than the remainder of the tube. When about four-fifths of the metal placed in A had distilled over, the tube was very slowly cooled. When cold, the tube was broken open, the portions in A and C being rejected in every case, while the metal was recovered from B in the form of a bar resting on the bottom of the tube, together with some crystal aggregates, suspended from the top and sides. A few crystal individuals were secured but the measurement of these will be considered later. The metal separated from the glass with a highly lustrous surface and did not attack the glass in the least.

The first distillation was effected in a tube bridged as represented in [Fig. 1], but drawn out at each end. The original cadmium powder was heated in the tube in a stream of pure hydrogen gas, for the purpose of obtaining the metal in the form of bars, and to reduce any cadmium oxide contained in the powder.

Six distillations were made in a vacuum. In the first, 630 grams of metal were used being distilled in quantities of about 130 grams each. At the end of the sixth distillation, there were about 100 grams of pure cadmium at disposal. In the fifth and sixth distillations, the metal was heated just above the melting point for from twenty to twenty-four hours, before being forced over into the middle portion of the tube. By this means all the remaining traces of the more volatile arsenic were driven into the front part of the tube and separated from the cadmium.

The distillations.

The residue represents the undistilled portion remaining in A. The distillate, the material obtained from B after the distillation was completed. The coating, the substance which condensed in C.

Residue,Cd, Pt, Zn,? As?.
Distillation IDistillate,Cd,   Zn,? As?
Coating,Cd,   Zn,? As?.
Residue,Cd, Zn?, As?.
Distillation IIDistillate,Cd, Zn?, As?.
Coating,Cd, Zn?, As?.
Residue,Cd, Zn?, As?.
Distillation III Distillate,Cd, Zn?, As?.
Coating,Cd, Zn?, As?.
Residue,Cd, Zn?, As?.
Distillation IVDistillate,Cd, Zn?, As?.
Coating,Cd, Zn?, As?.
Residue,Cd.
Distillation VDistillate,Cd.
Coating,Cd, As?.
Residue,Cd.
Distillation VIDistillate,Cd.
Coating,Cd.