Physical Properties of Palladium

Palladium may be prepared in several different physical states, namely, as the ordinary compact metal, as colloidal metal, as palladium sponge, and finally as palladium black. Of these, the last named is not pure palladium, but an indefinite mixture in a state of very fine division. Each of these varieties has its own peculiar physical characteristics.

Palladium is a silver-white metal, somewhat less ductile than platinum, but of equal or slightly greater hardness. It can be hammered into thin plates and drawn out into fine wire. It softens before reaching its melting-point, and can be welded below 1500° C. Its density is variously given, depending upon its physical condition, the values ranging from 11, 11.40 at 22.5° C. to 11.97 at 0° C. Hardness, 4.5 to 5.

Palladium melts at 1549.2° C. and boils at approximately 2540° C. It can be distilled in the electric furnace. It is less volatile than iridium, but more so than platinum. Its coefficient of linear expansion with rise of temperature is 0.0₄1176 between 0° and 100° C.; its specific heat between the same temperatures is 0.05928, and between 0° and 1300° C. the value may be calculated from the equation:

Specific Heat = 0.0582 + 0.000010t.

Molten palladium absorbs carbon, but on solidifying the latter element is thrown out in the crystalline form as graphite.

The most intense lines in the spectrum of palladium are as follow:

Arc: 3028.05, 3065.41, 3114.19, 3302.28, 3373.21, 3404.73, 3421.42, 3460.93, 3481.31, 3517.08, 3553.24, 3609.71, 3634.85, 3690.49, 3894.33, 3958.79, 4213.11, 5163.99, 5295.83, 5395.47, 5543.04, 5670.28, 6784.80.

Spark: 2776.95, 2854.70, 3404.80, 3421.41, 3481.34, 3517.11, 3553.21, 3609.70, 3634.83, 3894.39, 4213.16.