Voh. 7, 1921 
PHYSICS: E. H HALL 
105 
In columns II and III are given, in absolute units, the values of the 
potential gradient urging the associated electrons up the temperature 
gradient, at 0° C. and 100° C, respectively. P is potential due to elec- 
tric charge, and (dP/dT) seems open to electrostatic measurement. P a 
is potential due to differential attraction of the unequally heated metal 
for the associated electrons, and {dPjdT) does not seem within reach of di- 
rect experiment at present. Integrated from 0 ° C. to 100° C, d(P + P a )/dT 
gives differences of potential ranging from about 0.0026 volt in iron to a- 
bout 0.0065 volt in bismuth and in cobalt and about 0.008 volt in constantan. 
Column IV gives values of the "ionizing potential," in volts, within the 
metals at 0° C, and column V shows what these values would be at 
2727° C, or 3000° absolute, if the equation 
\' = y ' c + S RT 
held all the way to that temperature. 
Nothing exact can be expected from such an extrapolation, which takes 
no account of melting or of vaporization, but it is interesting to note that 
the values of 5 thus obtained are of the same order of magnitude as those 
found by direct experiment on the vapors of metals, though still somewhat 
smaller than .these latter values. 
Column VI shows, in calories, the amount of heat absorbed by the free 
ions and by the process of ionization in heating 1 cu. cm. of the metal 
1° C. in the neighborhood of 0° C. The former of these quantities is 
1.5Ryn, and the latter dn/dT.\ f = qriK'/T, each reduced to calories. 
Column VII gives the thermal capacity, per cu. cm., of the metals as 
found by experiment. 
Aluminium 
Bismuth 
Cobalt 
Copper 
Gold 
Iron 
Magnesium 
Molybdenum 
Nickel 
Palladium 
Platinum 
Silver 
Thallium 
Tin 
Tungsten 
Zinc 
Constantan 
Manganin 
10.5 
1.0 
4.9 
11 
11 
0 
11 
4. 
3 
2. 
2.9 
15.2 
1.8 
3.2 
1.9 
3.2 
0.7 
0.3 
II 
[ d(P + Pa) l 
dT J 0 
-4070 
-6620 
-6120 
-3970 
-4030 
-2530 
-3550 
-3540 
-5790 
-4720 
-4410 
-4050 
-3910 
-3700 
-4120 
-3720 
-7780 
-4180 
in 
L dT \ u 
■4050 
■6340 
■6920 
■3870 
■3940 
■2680 
■3550 
■3110 
■6160 
■5080 
■4680 
■3960 
■3960 
■3720 
■3770 
■3820 
■8590 
■4060 
IV 
8 at 
0°C. 
0.142 
0.169 
0.125 
0.162 
0.159 
0.348 
0.196 
0.197 
0.127 
0.160 
0.157 
0.169 
0.180 
0.179 
0.268 
0.178 
0.158 
0.228 
V 
S at 2727° C. 
1.46 
1.18 
1.35 
1.75 
1.72 
3.85 
1.78 
82 
73 
.92 
1.81 
1.71 
2.47 
VI 
0.212 
0.009 
0.139 
0.388 
0.260 
0.038 
0.224 
0.099 
0.093 
0.069 
0.078 
0.365 
0.027 
0.052 
0.072 
0.093 
0.024 
0.013 
VII 
0.54 
0.29 
0.86 
0.80 
0.60 
0.85 
0.40 
0.70 
0.89 
0.57 
0.67 
0.58 
0.36 
0.39 
0.64 
0.64 
0.85 
0.77 
