Now everyone knows alcohol thermometers. How did they come about, what types of these measuring instruments exist today and how are they used?
Modern thermometer prototype
It is believed that the father of the thermometer was Galileo Galilei. At the end of the 16th century, he created some semblance of a modern device called a thermoscope. It consisted of a cone and a glass tube and was designed to determine the fact of a change in water temperature. This device did not have a scale. Therefore, there was no way to find out how much she had changed.
Then the device was improved by adding a scale of beads, the air was removed, and turned upside down with a cone ball. Finally, the water was replaced with wine alcohol. This was done by the Florentine Torricelli. The innovation made it possible to take measurements in frosty weather. After all, when freezing, water not only did not move along the scale. The glass vessel itself burst and became unusable. In addition, the alcohol thermometer did not depend on atmospheric pressure. Several of the old Florentine thermometers have survived to this day and are in the Galileo Museum.
The divisions were applied to the tube with heated enamel, dozens in white, the rest in black. Range usuallywas from -10 to +40. The tube was filled with alcohol and sealed with sealing wax. Alcohol thermometers of one master showed the same values under equal conditions. But the divisions of each master were different. When trying to divide the scale into 100 or more parts, it was not possible to get the same values.
G. Fahrenheit invented to fill the thermometer with mercury. He recorded on the scale the freezing point of saline, 32 degrees Fahrenheit, 96 degrees body temperature, 212 freezing water. This thermometer was used until the middle of the 20th century, and continues to be used in the USA today.
Improvement of the thermometer
At the beginning of the 18th century, Guillaume Amonton changed the system of measurement. The Frenchman, who invented the alcohol thermometer, followed the change in air elasticity, not paying attention to pressure. In this case, the zero of the scale was the temperature, which is now called absolute zero. Another constant point in the thermometer was the boiling point of water. But the Frenchman who invented the alcohol thermometer did not take into account the effect of atmospheric pressure on the boiling point of water.
It looked like a siphon barometer with an open knee pointing up. Below was a solution of potash, and above oil. The reservoir has been sealed.
Temperature scales
This device is not very similar to modern alcohol thermometers for measuring temperature. At this time, many scientists were working on creating their own or improving existing models.
Another Frenchman improved the device. Réaumur's alcohol thermometer had a scale from 0 to 80 degrees. His ice melted at 0 degrees, and the water boiled at 80. He realized that mercury and alcohol expand differently, so the scales for thermometers must be different. But his thermometers were large and awkward to use.
From the middle of the 18th century to the 20th, several important discoveries were made. The Swede Anders Celsius accurately determined the boiling point of water to zero, and its freezing point to 100. It turned out that only the boiling point of ice depends on atmospheric pressure, and it does not affect freezing. Therefore, the divisions were arranged in this way.
There is no exact data on who exactly turned the scale upside down. Some say that Celsius himself did it. Other researchers attribute the reversal of the scale to Carl Linnaeus or Morten Strömer.
English scientist Kelvin (William Thomson) created an absolute temperature scale from absolute zero, on the Celsius scale it is -273.15 degrees.
In the 18th century, alcohol thermometers were widespread in Europe. They began to sell along with other goods. At that time, 19 temperature scales were already known. So, M. Lomonosov proposed his own, with 150, and Lambert - a scale with 375 divisions, each of which was equal to a thousandth of the expansion of air.
The 18th century was marked by significant discoveries in the field of creation and improvement of measuring instruments, including alcohol thermometers.
At the end of the 20th century begannew directions and devices appear, based on other principles of action.
Types of thermometers
- Liquid.
- Mechanical operate on the same principle, but instead of liquid, bimetallic bands or spirals are used.
- Electronic use the change in the resistance of the metal under the influence of temperature. As a conductor, platinum wire or sputtering on ceramics is used. Measures from -200°C to 850°C.
- Optical based on changing the level of the spectrum or other parameters. These include infrared body temperature meters that work without human contact.
- Gauge, expansion thermometers, pyrometric, thermoelectric.
Technical thermometers
These include instruments based on all kinds of measurements. They differ in increased adaptability to the conditions of use. These are agricultural, vibration-resistant and low-degree for special chambers, for oil products and laboratory. They are used for installation in pipelines, various tanks, in the chemical and food industries, in particular, in the processing of beets into sugar.
They are also used in private homes to control the temperature in various containers.
They can be vertical and angular. The name depends on the type of its lower part: it is straight or angular.
The principle of operation of industrial alcohol thermometers is based on the fact that the working solution expands or contracts under the influence of temperature.
Before you buythis measuring device, you need to familiarize yourself with its characteristics.
Technical alcohol thermometer can measure temperature from -70°С to 600°С.
Spirit thermometer up to 100 degrees is not suitable for canning. So, jam is considered ready when its temperature reaches 106 ° C. It will help to measure her alcohol thermometer for canning TK-1 or TK-110 in a metal case.
Filling thermometers
Liquid thermometers used to be filled with mercury and alcohol. But mercury vapor is very dangerous for the body. They form when you break a thermometer. Therefore, now mercury thermometers are practically not used.
Outdoor thermometers
Now large outdoor alcohol thermometers are becoming popular. Their length can reach 80 cm or more. They can decorate the wall of an office, shop or bank. A frame made of precious wood, plastic or metal looks rich and original. The porcelain stoneware scale is durable and reliable.
This outdoor alcohol thermometer measures temperatures from -53°С to 51°С.
The thermometer "Grape leaves" of the German company TFA Dostmann GmbH is made of forged iron. Can be used as outdoor or indoor. Length 385 cm.
Moller-Therm GmbH is one of the German companies. They manufacture high quality interior thermometers. They are guaranteed for 2 years.
More often used are home outdoor thermometers of a smallsize. They are attached to the window with Velcro or to the wooden parts of windows and doors with screws. Outdoor double-sided alcohol thermometers with Velcro with a scale that can be seen through the window glass are popular. After all, in order to find out the temperature on the street, you do not need to leave the apartment. One of the manufacturers is Penosil (Russia).
There are models with a plastic case.
Water temperature measurement
Alcohol thermometer can measure the temperature of the water in the baby's bath. To do this, it must be sealed in a plastic case.
Many are interested in whether it is possible to measure the temperature of water that boils with an alcohol thermometer? No, because alcohol boils at a lower temperature than water. But still there are specially calibrated and soldered thermometers with which you can do this. Therefore, use an alcohol thermometer up to 100 degrees Celsius. And for temperatures below zero, it is better suited than mercury. After all, mercury freezes at 39 degrees below zero. While alcohol can measure temperatures down to 70 degrees below zero.
