Everyone knows that temperature is measured in degrees Celsius. People who are familiar with physics know that the international unit of measurement of this quantity is kelvin. The historical development of the concept of temperature and the corresponding instruments for its determination has led to the fact that at present we use other metric systems than our ancestors. The article discusses the questions: what is the Reaumur degree when it was used and how it is connected with generally accepted scales for measuring temperature.
Renee Antoine Reaumur
Before considering the Reaumur scale for determining the temperature of surrounding bodies, consider the personality of its creator.
Rene Reaumur was born on February 28, 1683 in the French city of La Rochelle. He began to show love for scientific research of the surrounding world from early childhood. Rene was interested in physics, mathematics, astronomy, law, philosophy, biology, metallurgy, languages and many other disciplines.
At the age of 25, he becomes a member of the French Academy of Sciences, and they immediately begin to entrust him with the implementation of serious scientific projects of a national scale. As a member of the Academy of Sciences, every year for 50 years, Reaumur published a scientific work. Many of his works on the study of insects, as well as on the study of the properties of metals, were translated into English and German. Contemporaries called it Pliny of the 18th century.
Killed scientist at the age of 74 as a result of a fall from a horse during one of the horse rides. After himself, Reaumur left scientific manuscripts, which occupied 138 folders.
Opening a new temperature scale
At the beginning of the XVIII century in the world there was no universally accepted scale for measuring the temperature of bodies. In 1731, as a result of thermodynamic experiments, Rene Reaumur proposed the use of a temperature scale, which began to bear his name. This scale has been used for over 100 years in the leading countries of Europe, in particular, in France, in Germany and in Russia. In the end, it was supplanted by the Celsius scale, which is widely used to date.
It is curious to note that Reaumur proposed using his scale 11 years before Celsius did it.
The experiments that led to the invention of the Reaumur scale
The experiments that inspired the scientist to invent a new scale are very simple. They are as follows: Reaumur set himself the goal of measuring the transition temperature between the aggregate states of a liquid, which is vital for a person - water, that is, to determine when it begins to crystallize with the formation of ice, and when it begins to boil and passes into steam. For this purpose, the scientist decided to use an alcohol thermometer, which he constructed on his own.
The Reaumur thermometer was a glass tube about 1.5 meters high, which at the base expanded into a vessel about 10 cm in diameter. The tube was filled with a mixture of ethyl alcohol and water and sealed at both ends. It was the alcohol mixture that was chosen as the working fluid because this alcoholic substance has 4 times greater coefficient of thermal expansion than water. The latter fact means that the level of the alcohol column is very sensitive to temperature changes, so it can be used to accurately measure the value in question.
Having set the level of the alcohol column in the thermometer for 0 degrees, when its base is lowered into melting ice, Reaumur measured this value by placing the device in boiling water. The scientist noted that if the initial height of the alcohol column is 1000 units, then its final value is 1080 units. The number 80, as the difference between the hot and cold levels of a column in a thermometer, Reaumur put at the base of his temperature scale.
Eight Decimal Scale
As was said, 0 degrees on the Reaumur scale (° R) correspond to the melting point (melting) of ice, and 80 ° R corresponds to boiling water. This means that the scale proposed by the French scientist is eight-fold, which distinguishes it from the Celsius or Kelvin scales, which are based on the number 100. The latter fact, obviously, led to its gradual displacement by these scales. Our number system is decimal, so using digits of the order of 10, 100, and so on, is much more convenient than using intermediate values.
Connection with Celsius and Kelvin scales
As mentioned above, the temperature according to Reaumur is now not used almost anywhere, however, it is sometimes used during the cooking of sugar syrup and in the production of caramel. Therefore, formulas for translating degrees of Reaumur to Celsius and Kelvin should be given. These formulas are as follows:
- C = 1.25 * R;
- K = 1.25 * R + 273.15.
In the presented expressions, R, C, K are degrees of Reaumur, Celsius and Kelvin, respectively. Checking the correctness of the first formula is quite simple: substitute the value of 80 ° R, at which water boils. Then we get: C = 1.25 * 80 = 100 ° C, which exactly corresponds to the boiling point of this liquid under normal conditions in the usual scale for us.
We also give the inverse formulas for converting degrees Celsius and Kelvin to Reaumur:
- R = 0.8 * C;
- R = 0.8 * K - 218.52.
Note that zero degrees on the Reaumur scale coincides with this value of Celsius.
Problem solving example
As can be seen from the formulas of the previous paragraph, the transfer between different temperature measurement scales is quite simple. Let's solve a simple problem: "In the manufacture of caramel, a thermometer calibrated by degrees of Reaumur was used, which in the process of making sweets showed a value of 123 ° R. How many degrees would a thermometer show if it were calibrated to Celsius?"
We use the formula for converting degrees of Reaumur to Celsius, we get: C = 1.25 * 123 = 153.75 ° C. For completeness, we will also translate these degrees into Kelvin value, we get: K = 1.25 * 123 + 273.15 = 426.9 ° K.