Convert Delisle to Rankine faster than a falling thermomenter.

Ever tried reading an 18th-century Russian weather report or encountered thermodynamics equations using unfamiliar units? That's where Delisle to Rankine conversion comes into play. While not exactly an everyday conversion, understanding these historical and scientific temperature scales reveals fascinating stories about how humans measure heat. Let's explore this quirky temperature translation together.

Unit definitions

What is a Delisle (°De)?

The Delisle scale, created by French astronomer Joseph-Nicolas Delisle in 1732, has one of the most unusual temperature relationships. It starts at boiling water (100°C = 0°De) and increases as temperatures drop. By the time you reach water freezing, you're at 150°De. This inverse relationship made it popular in Russia for nearly a century before Celsius took over.

Symbol: °De
Common uses: Historical Russian meteorological records
Definition: 1°De = -2/3°C

What is a Rankine (°R)?

Rankine sits to Fahrenheit what Kelvin is to Celsius. Developed by Scottish engineer Macquorn Rankine in 1859, it's an absolute temperature scale where 0°R equals absolute zero (-459.67°F). While largely replaced by Kelvin in modern science, Rankine remains important in U.S. engineering systems, particularly thermodynamics.

Symbol: °R
Common uses: American engineering thermodynamics
Definition: 1°R = 1°F above absolute zero

Conversion formula

The mathematical bridge between these scales looks deceptively simple:
Rankine = 671.67 - (Delisle × 1.2)

This formula works because:

1. Delisle to Celsius: °C = 100 - (°De × 2/3)
2. Celsius to Kelvin: K = °C + 273.15
3. Kelvin to Rankine: °R = K × 9/5

Combining these steps removes the middle conversions:
°R = 100 - (2/3 × °De) + 273.15 × 9/5
Simplifies to our magic number: 671.67

Example calculations

Example 1: Convert 50°De to Rankine
671.67 - (50 × 1.2) = 671.67 - 60 = 611.67°R

Example 2: Convert 200°De to Rankine
671.67 - (200 × 1.2) = 671.67 - 240 = 431.67°R

Conversion tables

Delisle to Rankine

Rankine to Delisle

From tsarist Russia to space shuttles: A temperature journey

The Delisle scale's story begins with an astronomical miscalculation. Joseph-Nicolas Delisle originally created his scale for mercury thermometers, believing mercury expanded linearly with temperature (it doesn't). Despite this flaw, Russia adopted it in 1732 when Delisle founded the Saint Petersburg Observatory. For 102 years, Russian meteorologists recorded temperatures in Delisle degrees, creating thousands of historical records that modern climatologists sometimes need to convert.

Rankine's development 127 years later responded to industrial needs. As steam engines transformed transportation, engineers required absolute temperature measurements compatible with Fahrenheit. The Rankine scale became crucial for calculating engine efficiency, though its practical benefit diminished as metric standardization spread. Today, it survives in niche aerospace applications and some U.S. engineering textbooks.

Interesting facts

1. The Delisle scale remained Russia's official temperature standard longer than Celsius has been France's (adopted 1794)
2. At -240°De, mercury freezes. Delisle thermometers literally stopped working in Siberian winters
3. Rankine contains the same degree increments as Fahrenheit, making conversions between °F and °R simple (+459.67)
4. The coldest recorded temperature on Earth (-128.6°F) equals 331.07°R
5. Delisle's original scale had 2,400 degrees between boiling and freezing before he recalibrated it to 150°

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