BARUS.l 
PYRO-ELECTRIC PROPERTIES OF ALLOYS. 
Table 29.—- Density of platinum alloys— Continued. 
131 
No 
Alloy. 
Aluminium . , 
Manganese . . 
....do 
....do 
....do 
Molybdenum 
....do 
....do 
....do 
...do 
Lead 
...do 
....do 
Antimony ... 
....do 
Bismuth 
...do 
...do 
Zinc 
...do 
...do 
...do 
Cadmium 
12.00 
11.44 
11.44 
14.35 
14.34 
12.87 
14.36 
14.36 
13.76 
13.76 
16.86 
14.58 
14.57 
17.14 
17.14 
13.47 
15.02 
15.03 
13.33 
13.34 
12.29 
12.28 
12.22 
1262 
. 01296 
1298 
1287 
1287 
. 01320 
1298 
1296 
1223 
1225 
. 01278 
1212 
1213 
. 01343 
1340 
.01311 
1200 
1202 
01232 
1228 
1261 
1262 
1254 
3. 1388 
3. 0871 
3. 0872 
3. 5870 
3. 5867 
3. 6090 
3. 9585 
3. 9585 
3. 5869 
3. 5869 
4. 5626 
3. 7537 
3. 7539 
4. 7703 
4. 7703 
3. 7398 
3. 8495 
3. 8495 
3. 2990 
3. 2988 
3. 2496 
3. 2496 
3. 2667 
10.7 
11.2 
13.8 
11.4 
14.2 
14.6 
15.2 
11.8 
13.9 
18.4 
15.5 
13.0 
17.6 
15.8 
12.0 
16.1 
13.4 
17.8 
13.6 
18.2 
19.8 
20.0 
20. 715 
20. 814 
20. 779 
19. 412 
19. 434 
21. 250 
21. 239 
21. 260 
21.298 
21. 281 
21. 167 
21. 230 
21. 228 
20. 722 
20. 762 
21. 166 
21. 337 
21. 297 
20. 065 
20. 114 
20. 959 
20. 959 
Ao 
20. 724 
20. 823 
20. 790 
19. 421 
19. 445 
21. 263 
21. 252 
21.270 
21. 309 
21. 295 
21. 180 
21. 240 
21. 242 
20. 735 
20. 772 
21. 179 
21. 347 
21.311 
20. 076 
20. 128 
20. 975 
20. 975 
(21. 315) 
Ao 
Mean. 
20. 724 
20. 807 
19. 433 
21. 263 
21. 261 
21. 302 
21. 180 
21. 241 
20. 753 
21. 179 
21. 329 
20. 102 
20. 975 
Preliminary data, electrical resistance of rods. — Having given the 
values of A it is easy to measure the resistance of the bars of platinum 
illoy by carefully applying Matthiessen and Hockin's 1 or other similar 
nethod. The resistometer shown in Fig. 24, is so conveniently appli- 
cable that a short description may be given of it even if its principles be 
livell known. The appar atus may be made unusually compact by using 
Hohlrausch's admirable form of Wheatstone's bridge. In practice it is 
Conveniently inserted in the same circuit with the thermopile adjust- 
ment, and the two Daniells used as a source of current. All circuits 
ire to be made momentarily, of course. 
In Fig. 24 the Kohlrausch bridge is shown at A. B is the attach- 
ment for small resistances, D the standard with which they are to be 
Compared. Let s s be the small platinum rod to be tested. It is firmly 
jlamped down by the insulated levers m m, which properly insert it in 
he bridge circuits, m m and the similar levers nn, nn, may be moved 
*long a stout horizontal rod at pleasure, and then clamped in any po- 
sition. The part of ss to be electrically studied is stepped off by the 
ider e, the points of contact of which are knife edges at a known dis- 
tance apart. The rider is also capable of being slid along a horizontal 
>od, parallel to the rod carrying nn, etc. When in use e is held down 
*Cf. Maxwell: Electricity and Magnetism, 2d ed., 1881, p. 444. 
(785) 
