# Fahrenheit

### Gabriel Fahrenheit (1686 - 1736) was German and a Fellow of the Royal Society.

For all who prefer to use his temperature scale here is a little conversion poem:

If Centigrade confuse you,
As very well it might,
Nine-fifths of C, plus thirty-two
Will give you Fahrenheit.

### Fahrenheit's Zero

The standard temperature setting for the interior of domestic freezers is described as -18°C. At this temperature, bacterial activity is inhibited: life is at a standstill. It is thus the critical temperature for life at cellular level, and is (work it out!) at zero Fahrenheit: 0°F. Perhaps your friendly, local scientist should be told this fact of life!

# Did Fahrenheit get it right?

## by Donald Hammond

(Numbers preceded by an asterisk [*] are dozenal)

Gabriel Daniel Fahrenheit (1686-1736) is a name today much maligned. For years, scientists (who should, perhaps, know better) have spoken of his temperature scale in terms of patronising disparagement; now, the metric trendies are trying to consign oF to oblivion. ITV, for example, contemptuous of what its viewers might find useful, will not give even the Fahrenheit equivalent of their Centigrade figures, although the BBC does sometimes give a vague Fahrenheit reference in the course of weather forecasts and reports. I should like to suggest that, for people in general and dozenists in particular, a modified Fahrenheit scale of temperature has a great deal to offer in terms of fineness and practicality.

A very brief historical sketch may be instructive. Isaac Newton, apparently, made some sort of thermometer with fixed points at the temperature of melting ice (ice point) and that of the healthy human mouth. Newton divided the range between these points into twelve equal divisions! (That, in itself, is significant: a man of great intellect, revered by scientists the world over, chose to divide a brand-new scale into twelve, not ten. Is anybody going to tell us that Newton did not understand measurement or mathematics?)

Probably some time between 1710 and 1720, Fahrenheit, determined to design a thermometric scale suitable for atmospheric (weather) temperatures, experimented with freezing-mixtures: ice and sal-ammoniac; ice and sea-salt; etc., until he got the lowest reading (which might reasonably be expected in Polar seas, due to eutectic reactions between salt water and ice) and called it zero. There is no reason to suppose that Fahrenheit thought this to be the lowest temperature possible: this was a zero intended for practical use in Earth's environment. The range between this zero and human body temperature he then divided into two dozen equal parts (again, note the thinking) which gave the ice point for fresh water at one-third of the range, or eight degrees. However, these 'degrees' seemed rather coarse in practice, so Fahrenheit multiplied their number by four, thus making human body temperature 96°F (Note1) and the ice point 32°F. Subsequently, the temperature of boiling water (steam point) was found to be 212°F on the same scale. So, the range between ice point and steam point of fresh water is l80 Fahrenheit degrees.

Reaumur, some time later, had the sensible idea that a more practical zero would be at the ice point; he set the steam point as 80°Reaumur because he found the expansion ratio of his thermometric liquid (alcohol and water mixed 4 : 1) was 1000 : 1080 between the fixed points.

Celsius, in 1742, is said to have made a "great contribution" by division of the range into l00, although his first notion was to have it upside-down: boiling water = 0°C, freezing water = 100°C! To quote the author of a schools science text: "His great contribution was division of the scale into 100 degrees, instead of some odd (sic) number of parts as Fahrenheit and Reaumur had done." It takes a really blinkered mind to assert that 100 is a more useful number than 180, and that 180 is an odd number!

### ABSOLUTE TEMPERATURE

For most purposes (Note 2), absolute zero is -273°C and -460°F in decimal terms. At this level, there is no heat present in a substance: molecular motion ceases altogether. Absolute temperature scales, therefore, use absolute zero as zero: if Centigrade degrees are used, the absolute scale is in oKelvin; if Fahrenheit degrees, then in °Rankine. Thus, in absolute terms, the temperature of melting ice is 273°K or 492°R; of boiling water, 373°K or 672°R.

### A RATIONAL FAHRENHEIT SCALE

Reaumur's notion of setting a conventional zero at the freezing-point of fresh water was a useful one; Fahrenheit's range of l80° from ice to steam is excellent numerically and gives reasonably fine divisions. Let us, therefore, combine these two desirable features into one temperature scale for common use. It can be called 'Rational Fahrenheit' and use the symbol "rF". In decimal terms, our new ice point is 0rF, new steam point is 180rF and (nominal) absolute zero is -492rF. (Note that on this Scale, the hottest places on Earth approach 100rF; the British Thermal Unit, used here and in the USA, remains unchanged).

The real bonus, for me, is that this proposed scale can be converted to dozenal notation with an actual gain in simplicity: ice point = 0rF; steam point = *130rF and absolute zero = -*350rF dozenally. The absolute scale in dozenal is: zero = 0rR ; ice point = *350rR and - wait for it - the steam point = *480rR! Now, if anyone can find nicer "round" numbers than these for absolute zero and the two fixed points for water, I should like to know!

### TEMPERATURE SCALES COMPARED

For general use:

PointCelsiusFahrenheitRational Fahrenheit
decimaldozenal
Steam point100212180*130
Ice point03200
Absolute zero-273-460-492-*350

Note that the conversion equation relating C and F now becomes simpler:
F/C = 9/5, because of agreement at the ice point, and will do for both actual temperatures and temperature changes

Absolute scales:

PointKelvinRankine*Rankine
Steam373672*480
Ice273492*350
Zero000

Here, then, is a possible scale of temperature which retains the virtues of the Fahrenheit scale; which makes calculation easier; and which fits dozenal numeration like a glove!

Notes:

Note1: Later, more accurate thermometers, involving less loss of heat, showed this to be 98·6.

Note 2: Truer values are: -273·16°C, -459·69°F. The exact values are a highly theoretical matter.

References:

• Gregory & Hadley: "A Class Book of Physics" l92O
• Stone,Bronner, Lawrence: "Heat & Light" 1955
• John B.Sandfort: "Heat Engines' 1961
• Oliver Lyle: "The Efficient Use of Steam." 1947
• Uvarov & Chapman: "A Dictionary of Science" 1971

# At Boiling Point

## by Paul Jennings

I cannot prove this, but I just know that the two figures which even the least numerate people in the country could reel off automatically (not having actually learnt them at all, but having simply absorbed them somehow from the national air) are 1066 and 98·4. The Battle of Hastings (really the Battle of Battle - all right, then, Senlac, six miles from Hastings, since that is where they fought) and normal body temperature - in degrees Fahrenheit.

I bet not one in a hundred readers of this article knows what normal is in Centigrade - or "Celsius" - as they have recently taken to saying on television. In fact, I bet it does not even tell you in all the Buff they give you when you take the car to the Continent - the Green Card, and all that stuff in eight languages about trouble with the car (extraordinary how "your clutch needs relining" sounds like one of the more mournful Schubert 'lieder' in German -'Die Kupplung muss neu belegt werden' - while in Denmark, all meadows and cows and pigs and timbery farms and green copper spires, it is 'Koblingen traenger til at blive efterset', which sounds like some dreadful oath. "What's the trouble dear?" says your wife, as you return, black-faced, from the garage. "Ah, blive EFTERSET!" you reply, flinging a spanner on the ground).

Maybe it is because the thing is intimate and personal - dash it all, what could be more so than the question of whether one's own body is normal or feverish? - that Centigrade (or Celsius) is the very last bit of the compulsory EEC decimal system to have the slightest significance or reality for us of the good old pounds-shillings-and- pence generation. Half-a-crown, a guinea, a tanner, a bob, even a pound note - these were heavy with centuries of use behind them; real things, compared to which expressions like "fifty pee" will always seem an unreal abstraction.

Or take length. A metre, says the 'Dictionary of Scientific Units', "is defined in terms of the orange (2p10-5d5) line emitted by a krypton (Kr86/30) discharge in an Engelhard hot cathode discharge tube enclosed in a cryostat at the triple point of nitrogen (63oK); one metre is represented by 1,650,763·73 vacuum wavelengths of this light"/

Now they tell us. Those Jacobin madmen in their red nightcaps who cooked up this whole metric thing in 1793 did not know about krypton, any more than the few scientists whose heads had not been cut off and who mumbled something about the unit of length being "10-7 of the earth's quadrant passing through Paris" and got this platinum bar kept in some vault which was THE metre - just because they decided to say so. Abstract, you see: whereas our yard comes from the Old English gierd or gyrd, a stick; and foot comes from, well, the length of a man's foot. What could be more physical and real than that?

Duodecimal. too. The 24-hour day. which we still have, goes back to the Babylonians and Sumerians, who saw the point of a number you can divide by 2, 3, 4 and 6 - not just 2 and 5. And even the French had twelve months in their new calendar (which Carlyle, of all people, translated so wittily: Vendemiaire, Vintagearious; Brumaire, Fogarious; Frimaire, Frostarious; Nivose, Snowous; Pluviose, Rainous; Ventose, Windous; Germinal, Buddal; Floreal, Floweral; Prairial, Meadowal; Messidor, Reapidor; Thermidor, Heatidor; and Fructidor, Fruitidor).

Before Dismalization we were always being told that we should be left behind in the international technological race if we did not adopt it. But the Americans have put men on the Moon and can hit a tin can or a missile with a three-inch nail from 3,000 miles up in space, and they still have gallons, miles, pounds and no intention of changing.

But none of these is so sadly missed as Fahrenheit. That in itself proves there is nothing insular about us, for it is clearly German, yet with an air of universality about it.

It does not matter so much that we do not think of that little bottle of beer as 275 millilitres, but still as some kind of half-pint; or that we always have to check whether it is about two-and-a-half lb to the kilo or two-and-a-half kilos
to the lb; but it does matter if the weather man on television does not add the Fahrenheit equivalent in a kind of spoken brackets.

The other temperature scale, Reaumur, with its great clumsy degrees (only 80 from freezing to boiling, compared with Fahrenheit's 180) can be dismissed altogether. It does not sound like a man; more like a small town in northeast France, with a Second Division football team (Limoges 3, Reaumur 1). But Fahrenheit, the man I always put with all those other German chemists brilliantly synthesising indigo and such things in the 19th century, having names like Pfunzl, Hoffmeyer, Bayer or Stumpff. Celsius sounded earlier: one foot in medieval alchemy, the other in the Renaissance.

It turns out to be the other way round. Anders Celsius, 1701-44, was Swedish. Gabriel (Gabriel!) Fahrenheit, 1686-1736, was German and a fellow of the Royal Society. Well, rather Celsius than Centigrade (even if they are the same); and rather Fahrenheit than either of them. Bring him back!

(This article © 1986 Telegraph Sunday Magazine, and reprinted by permission in the Dozenal Journal no. 4 of the DSGB).

Editor's note: readers interested in the history and possible development of temperature scales are referred to Dozenal Review No.*32 or Dozenal Journal No. 1.