vod: 
§ 8 An idea of the degree of purity of the lead is obtained from 
the values which we give here for the resistance at various temperatures. 
eck Lik oi 
Resistance of the lead wire 
Pb} at low temperatures. 
T w 
289° K 12.75 2 
— 90° 3.77 
202: 0,125 
IPS 0.626 
149.5 0.520 
Comparison of these values with those given by KAMERLINGH ONNES 
and Cray, Comm. No. 99¢, shows that the lead now used must hold 
in solid solution a fairly considerable amount of foreign matter, for 
the great change in the temperature coefficient exhibited by metals 
in the presence of small amounts of impurity may generally be 
attributed to the transition of this admixture to a state of solid solution. 
Our measurements were made with liquid oxygen and liquid hydro- 
gen as compressing liquids. The results are contained in Table II. 
The pressure (p) is given in atmospheres. 
BAB GE IL, 
Change induced in the resistance of lead 
Pb, by compression at low temperatures. 
7 = 900 kK T = 20°.3 K 
A TEE A TEN 
W = = A WwW 
P A Perr Ë IT: 
49.4 |— 0.0043 n'— 2.35 X 10-—5! 49.7 — 0.00062 | — 1.7X10-—5 
Piel 0.0080 — |= 2:2 dT |= 0 0OL A ka 
102.5 |— 0.0085 '— 2.2 OLS |— 0.00182) EEE 
48.5 |\—.0.0040 |— 2.3 98 125000415 IB 
ror 142 7.j0719 i 9:2 97.5 — 0.00131 tg 
01.510 00114 PEA tad 
62% 
