File:The London, Edinburgh and Dublin philosophical magazine and journal of science (1898) (14597292047).jpg

Identifier: londonedinburgh5451898lon (find matches)
Title: The London, Edinburgh and Dublin philosophical magazine and journal of science
Year: 1840 (1840s)
Authors:
Subjects: Science
Publisher: London : Taylor & Francis
Contributing Library: Smithsonian Institution Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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thoseobtained by the above method (§69). These and otherdetails are noted on the diagram. § 77. The diagram on p.428 gives the temperature-variationsof all the substances studied. The curves in it are plotted bytaking the results for each metal of those experiments whichare most free from all complication or cause of doubt. If thecurves be prolonged in the direction of lower temperaturethey appear to meet somewhere below -200° C, and prob-ably asymptotically to the line representing *4 v. positive tostandard plate at 16° C. Within their range they showcontact-potential-differences diminishing with lowered tem-perature. The only apparent exceptions are clean copper,and silver coated with glass ; but both their curves aredistinctly bent between 16° C. and 50° C, so that probablythey are directed towards the same point as the others atower temperatures. Thus it appears that at about — 200° C.the contact-potential-differences of metals may vanish, and 428 Dr. J. Erskine-Murray on
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/o° 20° So* 4o* 6ov cov 70v do*Temperature, Centigrade. Volta Electricity of Metals. 429 that a plate of any metal at that temperature would be about4 volt positive to a standard gold plate at 16° C. § 78. The approximate numerical values of the temperature-variations are given in the following table :— Table V. Metal. Approximate range ofTemperature. Potential of metal with standard gold plate. Both at 16° C. Variation of potential per 1° C. Standard plate kept always at 16° C. Aluminium, polished on glass-paper,, waxed °C.16-5016-4016-4715-6216-7516-3316-5516-6516-6016-7016-3030-5016-3030-6016-6016-65 Volts.+ 1-10+ -98+1-30+ -73+ -58+ -52+ -20+ -28+ -12+ -16 - -05 + -04 •00 - 11 Volts.+•0043+ •0032+ •0045+ •0013+ •0016 About --0010-•0022-•0007-•0007-•0004 About --0035 About --0110Very small. About +-0015-•0016-0016 „ alcohol-washed, dry ...Zinc, polished on glass-paper i Lead, scraped Tin, polished on glass-paper Iron, polished on emery-cloth„ alc

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