Triple point of water to Newton
TPW
N
Conversion History
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Quick Reference Table (Triple point of water to Newton)
| Triple point of water (TPW) | Newton (N) |
|---|---|
| 0 | -90.1395 |
| 0.9999 | -0.005714153452164671448 |
| 1 | 0.0033001265604913776918 |
| 1.073 | 6.5837245357994072482608 |
| 1.136 | 12.2627209437727182050577 |
| 1.366 | 32.9955649728816312219249 |
About Triple point of water (TPW)
The triple point of water is a fundamental thermometric reference: the unique temperature and pressure (273.16 K, 611.657 Pa) at which water coexists simultaneously as solid, liquid, and vapor. When used as a temperature unit, one triple-point unit (TPW) equals 273.16 K, so temperatures are expressed as multiples of this fixed point. This makes 0 TPW equal to absolute zero and 1.000 TPW equal to water's triple point exactly. The freezing point (273.15 K) is 0.9999 TPW — just below 1 — while boiling (373.15 K) is approximately 1.366 TPW. This unit served as the defining reference for the kelvin from 1954 until the 2019 SI revision.
Used in metrology laboratories to calibrate precision thermometers. A sealed triple-point cell containing ultra-pure water held at exactly 273.16 K (0.01°C) serves as a primary temperature standard.
About Newton (N)
The Newton scale is an obsolete historical temperature scale proposed by Isaac Newton around 1701, predating both Celsius and Fahrenheit. It sets 0°N at the freezing point of water and 33°N at the boiling point — a 33-degree span. Newton chose 33 because it divides cleanly into thirds and twelfths, reflecting duodecimal arithmetic conventions of the time. Body temperature is approximately 12.2°N. Newton calibrated his scale using linseed oil as the thermometric fluid. His scale influenced later thermometrists but was never widely adopted and is today of primarily historical and educational interest, appearing in scientific history discussions and temperature conversion tools.
Body temperature (37°C) is approximately 12.2°N on Newton's scale. A warm summer day of 25°C equals about 8.25°N.
Etymology: Proposed by Isaac Newton (1643–1727) in his 1701 paper "Scala Graduum Caloris" (Scale of the Degrees of Heat), published anonymously in Philosophical Transactions. Newton used a linseed oil thermometer and calibrated it against the freezing point of water and body temperature, later extending it to a second reference at the boiling point.
Triple point of water – Frequently Asked Questions
What is the triple point of water?
The triple point of water is the unique combination of temperature and pressure (273.16 K / 0.01°C and 611.657 Pa) at which water can coexist as solid, liquid, and gas simultaneously. It is a fixed thermodynamic point that cannot vary — any change in temperature or pressure causes one phase to disappear.
Why was the triple point of water used to define the kelvin?
The triple point is a perfectly reproducible, invariant temperature — it occurs at exactly one pressure and temperature. From 1954 to 2019, the kelvin was defined as 1/273.16 of the thermodynamic temperature of the triple point of water, providing a stable international calibration reference accessible to any metrology lab.
What is the difference between the triple point and the freezing point of water?
The freezing point of water at standard atmospheric pressure is 273.15 K (0.00°C), while the triple point is 273.16 K (0.01°C) at 611.657 Pa. The triple point is 0.01°C warmer and occurs at much lower pressure than normal atmospheric conditions. Both are distinct and precisely defined reference points.
What replaced the triple point of water in the 2019 SI redefinition?
In the 2019 redefinition of SI units, the kelvin was redefined by fixing the value of the Boltzmann constant (k = 1.380649 × 10⁻²³ J/K) exactly. This makes the kelvin independent of any physical substance, more stable, and consistent with other SI redefinitions that fixed fundamental constants rather than relying on material artifacts.
Can the triple point of water occur naturally?
The triple point requires a pressure of about 611 Pa — roughly 0.6% of standard atmospheric pressure. On Earth's surface this does not occur naturally. On Mars, where atmospheric pressure is around 600–700 Pa at the surface, conditions near the triple point of water can occur, meaning liquid water, ice, and water vapor can briefly coexist on the Martian surface under the right conditions.
Newton – Frequently Asked Questions
Who invented the Newton temperature scale?
Isaac Newton proposed the scale in 1701 in his paper "Scala Graduum Caloris", published anonymously in Philosophical Transactions of the Royal Society. He used a linseed oil thermometer and calibrated it against the freezing point of water and body temperature as fixed reference points.
What are the reference points of the Newton scale?
0°N is the freezing point of water and 33°N is the boiling point of water, giving a 33-degree range. Newton also used body temperature (approximately 12°N) and "the greatest summer heat" as intermediate calibration points. These are the same two endpoints used by later scales, just with different degree spans.
Why did Newton choose 33 degrees for boiling water?
Newton chose 33 because it factors neatly: 33 = 3 × 11, and one-third of 33 (11°N) corresponds approximately to body temperature in his calibration. The choice reflects his preference for divisions into thirds and twelfths, common in pre-metric scientific notation, rather than the decimal basis used by Celsius.
How does the Newton scale compare to Celsius?
Newton and Celsius share the same zero (freezing water = 0), but Newton's boiling point is 33°N versus 100°C. To convert: °N = °C × 33/100 (or × 0.33). Room temperature (20°C) is 6.6°N; body temperature (37°C) is 12.21°N.
Is the Newton temperature scale still used today?
No. The Newton scale was never widely adopted and fell out of use by the mid-18th century as Fahrenheit and Celsius became dominant. It survives today only in historical accounts of thermometry and in temperature conversion tools as an educational curiosity about the origins of quantitative temperature measurement.