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Pt has relatively less affinity to oxygen compared to other Pt-group metals, but it
generates an oxide film by heating for 1 week with oxygen at 520¡É.
This can be removed by high-temperature heating or hydrogen reduction. In the
meanwhile, Rh is converted to RhO by heating with oxygen or air at 600~1000¡É
and gradually changed to a mixture of Rh2O3 and Rh.
The color of Rh is changed gradually to be black and green at 600~700¡É, to be
purple at 900~1000¡É, and finally be a gray over than 1150¡É due to heat
degradation of oxide. |
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It is double for Rh that the vaporizing amount of Pt in the air at 1300¡É, 1/3 of Pd,
1/13 of Ir, and 1/100 of Ru, and it becomes decrease by progressing vacuum.
The vaporizing amount is very tiny under nitrogen gas and also measurelessly little
under the condition of hydrogen.
From these, it is proved that Pt is well vaporized with the oxygen.
The vaporizing amount of Pt under the oxygen is 5 folds to that of air, and 2 folds
for 760mmHg to that of 25 mmHg. |
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| Temperature |
Pt |
Pt-Rh 10% |
Pt-Rh 20% |
Pt-Rh 40% |
| ¡É |
¢µ |
Microhm
§¯ |
Ohm
§¯ |
Microhm
§¯ |
Ohm
Cir.Mill.Ft |
Microhm
§¯ |
Ohm
Cir.Mill.Ft |
Microhm
§¯ |
Ohm
Cir.Mill.Ft |
| 20 |
68 |
10.8 |
65 |
19.2 |
115 |
20.8 |
125 |
17.4 |
105 |
| 1000 |
1830 |
41.5 |
250 |
46.6 |
280 |
43.3 |
260 |
40.0 |
240 |
| 1200 |
2190 |
46.5 |
280 |
51.4 |
325 |
50.0 |
300 |
- |
- |
| 1300 |
2370 |
49.0 |
295 |
54.1 |
325 |
50.0 |
300 |
- |
- |
| 1400 |
2500 |
50.5 |
305 |
55.3 |
335 |
51.6 |
310 |
- |
- |
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| Elementary Symbol |
Pt |
Pt-Rh 10% |
Pt-Rh 20% |
Pt-Rh 40% |
| M.P.(¡É) |
1,769 |
1,850 |
1,885 |
1,963 |
| Density (g/§¨) |
21.45 |
20.1 |
18.1 |
12.40 |
| Hardness (Hv) |
45~55 |
85~95 |
105~115 |
95~110 |
Coefficient of
thermal expansion
(1,000¡É) |
1.01019 |
1.01060 |
1.0099 |
1.01000 |
Resistivity (§Ùcm)
(1,000¡É) |
41.6 |
46.5 |
43.4 |
- |
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It is shown in following graphs that the relationship between the borosilicate crown glass
of Pt, PtRh, PtAu, and PtRhAu alloy and contact angle. In comparing around 1200¡É, the
contact angle for Pt is correspond to 20¡Æand PtRh10 is 40¡Æ, respectively.
In addition, the more density of Pt-Au alloy the larger contact angle. |
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