Everyone knows that temperature is measured in degrees Celsius. People who are familiar with physics know that the international unit of this quantity is the 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 Réaumur degree, when was it used and how is it related to the generally accepted scales for measuring temperature.
Rene Antoine Réaumur
Before considering the Réaumur 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 he immediately begins to entrust the implementation of serious scientific projects on a national scale. As a member of the Academy of Sciences, Réaumur published a scientific work every year for 50 years. 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. His contemporaries called him Pliny of the 18th century.
The scientist died at the age of 74 as a result of a fall from a horse during one of the horse rides. After himself, Réaumur left scientific manuscripts that occupied 138 folders.
Opening a new temperature scale
At the beginning of the 18th century, there was no generally accepted scale for measuring body temperature in the world. In 1731, as a result of thermodynamic experiments, Rene Reaumur proposed the use of a temperature scale, which began to bear his surname. This scale has been used for more than 100 years in the leading countries of Europe, in particular, in France, Germany and Russia. It was eventually superseded by the Celsius scale, which is still widely used today.
It is interesting to note that Réaumur proposed using his scale 11 years before Celsius did.
Experiments that led to the invention of the Réaumur scale
The experiments that inspired the scientist to invent a new scale are very simple. They are as follows: Réaumur set himself the goal of measuring the transition temperature between the states of aggregation of a vital liquid for humans - water, that is, to determine when it begins to crystallize with the formation of ice, and when it begins to boil and turns into steam. For this purpose, the scientist decided to use an alcohol thermometer, which he designed himself.
Reaumur's thermometer was a glass tube, about 1.5 meters high, which expanded at the base into a vessel with a diameter of about 10 cm. 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 a 4 times higher 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 quantity in question.
Setting the level of the alcohol column in the thermometer at 0 degrees when its base is lowered into melting ice, Réaumur measured this value by placing the device in boiling water. The scientist noticed that if the initial height of the column of alcohol 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, Réaumur put at the base of his temperature scale.
octal scale
As it was said, 0 degrees on the Réaumur scale (°R) correspond to the melting (melting) temperature of ice, and 80 °R to the boiling point of water. It means,that the scale proposed by the French scientist is eighty-decimal, 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 numbers like 10, 100, and so on is much more convenient than intermediate values.
Relationship with Celsius and Kelvin scales
As mentioned above, Réaumur temperature is not used almost anywhere now, however, it is sometimes used during the preparation of sugar syrup and in the production of caramel. Therefore, the formulas for converting Reaumur degrees to Celsius and Kelvin should be given. These formulas are as follows:
- C=1, 25R;
- K=1, 25R + 273, 15.
In the presented expressions R, C, K - degrees Réaumur, Celsius and Kelvin, respectively. Checking the correctness of the first formula is quite simple: we substitute into it the value of 80 ° R, at which water boils. Then we get: C \u003d 1, 2580 \u003d 100 ° C, which exactly corresponds to the boiling point of this liquid under normal conditions in the scale familiar to us.
Also, here are the inverse formulas for converting degrees Celsius and Kelvin to Réaumur:
- R=0.8C;
- R=0.8K - 218.52.
Note that zero degrees Réaumur coincides with this Celsius temperature.
Example of problem solving
As can be seen from the formulas of the previous paragraph, the conversion between different measurement scalestemperature is easy enough. Let's solve a simple problem: "In the manufacture of caramel, a thermometer calibrated to Réaumur degrees was used, which, during the preparation of sweets, showed a value of 123 ° R. How many degrees would the thermometer show if it were calibrated to the Celsius scale?"
Use the formula for converting Réaumur degrees to Celsius, we get: C=1.25123=153.75 °C. For completeness of the solution, we also translate these degrees into a Kelvin value, we get: K \u003d 1.25123 + 273, 15 \u003d 426.9 ° K.
