Now everyone knows alcohol thermometers. How did they arise, what types of these measuring instruments are currently available, and how are they used?
The prototype of a modern thermometer
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 intended to determine the fact of a change in water temperature. There was no scale for this device. Therefore, it was not possible to find out how much it had changed.
Then the device was improved, adding a scale from the beads, air was removed, the bulb was turned upside down. 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, water during freezing not only did not move along the scale. The glass vessel itself burst and became worthless. In addition, the alcohol thermometer was independent of atmospheric pressure. Several of the old Florentine thermometers have survived to the present day and are in the Galileo Museum.
The divisions were applied to the tube with heated enamel, dozens in white, the rest in black. The range was usually from -10 to +40. The tube was filled with alcohol and sealed with 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.
To fill the thermometer with mercury was invented by G. Fahrenheit. 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 in the USA they continue to be used now.
Thermometer improvement
At the beginning of the XVIII century, Guillaume Amonton changed the measurement system. The Frenchman, who invented an alcohol thermometer, monitored 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 an alcohol thermometer, did not take into account the influence 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 was oil. The tank was sealed.
Temperature Scales
This device is not very similar to modern alcohol thermometers for measuring temperature. At this time, many scientists worked on creating their own or improving existing models.
Another Frenchman improved the device. The alcohol thermometer Reaumur 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, because the scales for thermometers should be different. But his thermometers were large and inconvenient to use.
From the middle of the 18th century until the 20th, several important discoveries were made. The Swede Anders Celsius accurately determined the boiling point of water as zero, and its freezing point as 100. It turned out that only the boiling point of ice depends on atmospheric pressure, but it does not affect freezing. Therefore, the divisions were located that way.
There is no exact data about exactly who turned the scale upside down. Some say that Celsius himself did it. Other researchers attribute the change in direction of the scale to Karl Linnaeus or Morten Stremer.
The 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 be sold along with other goods. At that time, there were already 19 known temperature scales. 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 air expansion.
The 18th century was marked by significant discoveries in the field of the creation and improvement of measuring instruments, including alcohol thermometers.
At the end of the 20th century, new directions and devices began to arise, based on other principles of action.
Types of Thermometers
- Liquid.
- Mechanical ones act on the same principle, but bimetallic tapes or spirals are used instead of liquids.
- Electronic use a change in the resistance of a metal under the influence of temperature. As a conductor, platinum wire or ceramic spraying is used. Measure from -200 ° C to 850 ° C.
- Optical based on a change in the level of the spectrum or other parameters. These include infrared body temperature meters that work without human contact.
- Manometric, expansion thermometers, pyrometric, thermoelectric.
Technical thermometers
These include instruments based on all types of measurements. They are distinguished by increased adaptability to the conditions of use. These are agricultural, vibration-proof and low-degree for special cameras, for petroleum 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 for temperature control in various containers.
They can be vertical and angular. The name depends on the type of its lower part: straight or angular.
The principle of operation of alcohol technical thermometers is based on the fact that the working solution expands or contracts under the influence of temperature.
Before buying this measuring device, you need to familiarize yourself with its characteristics.
A technical alcohol thermometer can measure temperatures from -70 ° C to 600 ° C.
An alcohol 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 its 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 to the body. They are formed if you break a thermometer. Therefore, mercury thermometers are practically not used now.
Outdoor thermometers
Now large outdoor alcohol thermometers are becoming popular. Their length can reach 80 cm and more. They can decorate the wall of an office, store or bank. The frame made of precious wood, plastic or metal looks rich and original. The scale of ceramic granite is durable and reliable.
Such a street alcohol thermometer measures the temperature from -53 ° C to 51 ° C.
The grape leaves thermometer of the German company TFA Dostmann GmbH is made of wrought iron. It can be used as external or internal. Length 385 cm.
German companies include Moller-Therm GmbH. They make high quality interior thermometers. The warranty on them is 2 years.
Often used small home outdoor thermometers. They are attached to the window with Velcro or to the wooden parts of windows and doors with screws. Velcro outdoor double-sided alcohol thermometers are popular with a scale that can be seen through the glass of the window. 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
An alcohol thermometer can measure the temperature of the water in the bathtub for bathing a child. To do this, it must be sealed in a plastic case.
Many are interested in whether it is possible with an alcohol thermometer to measure the temperature of the water that boils? No, because alcohol boils at a lower temperature than water. But still there are specially calibrated and sealed thermometers with which you can do this. Therefore, they use an alcohol thermometer up to 100 degrees Celsius. And for temperatures below zero, it is better than mercury. After all, mercury freezes at 39 degrees below zero. While alcohol can measure temperatures up to 70 degrees below zero.