A refractometer is a portable optical-mechanical device, without power sources, with a minimum amount of sample, in a few seconds, measuring the concentration of substances dissolved in a liquid using a light beam.
The name of the device is a composite of “refracto” and “meter”, which to a first approximation explains the principle of operation of a refractometer, if we remember about refraction or bending of light.
And if you can’t remember, let’s take a closer look at the pictures, and you will understand that despite the strict and sonorous name, a refractometer is an optical instrument that even a schoolchild can work with.
But first, a few words about where is it in demand? manual refractometer who keeps in their arsenal a stylish, reliable and portable measuring device, which does not need batteries or power at all, but all it needs is light.
Optics with wide range applications, useful and in demand during all 4 seasons of the year - a hand-held refractometer, in the laboratory, in the apiary, in the garden, garage, warehouse, involved at all stages, from production to sale finished products.
Let's explain with an example.
Let's say you want to measure the sugar content of fruit juice. Everyone wants to enjoy sweet apples, plums and pears!
Depending on the degree of ripeness of the fruit, the concentration of sucrose will increase, and the harvest time, conservation costs, and, of course, the taste preferences of buyers - and therefore demand, price and the final financial result - depend on this.
A gardener, of course, can periodically eat one fruit for analysis, but relying on the subjectivity of taste buds is at least frivolous.
Nobody canceled laboratory tests.
Prepare special glassware, reagents, invite qualified personnel, purchase furniture, equipment, supply electricity and, most importantly, reserve time.
Chemical research is clearly not the fastest method of analysis.
In addition, let us pay attention to 3 more factors.
Eat Alternative option much faster and cheaper - the price of which is several times less than the average monthly salary.
A refractometer is a lightweight, compact and high-speed measuring device that allows you to avoid mistakes, identify dangerous trends in a timely manner, save financial resources in the budget of a company or family, make money on sales, and preserve the integrity of industrial equipment and support on high level business reputation in business.
* The Brix scale is a globally recognized measure of measuring the concentration of substances dissolved in a liquid (as a percentage)
The first thing you need to know is that a refractometer is a portable optical measuring instrument.
The operating principle of the refractometer is based on original method using the phenomenon of light refraction to measure the concentration of a solution.
Figuratively speaking, the operating principle of an optical measuring device is based on the synergy of two sciences, the quintessence of 4 words: “physics of light + chemistry of solution.”
The analyzed solutions consist of at least two components - a solvent and a solute. As the liquid becomes saturated, the density and optical permeability to light rays change. This is the first "trick".
Sunlight or stream artificial lighting pierce both the air around us and optically transparent objects, including glass and water.
The beam sequentially passes from one medium to another and at the boundary a practically important physical effect of refraction is observed - the curvature of the direction of movement of light. This is the second “trick”, thanks to which the refractometer readings become a reality.
The picture shows a lens - solid, but a similar phenomenon is observed in liquids and even in the atmosphere. It is not the state of aggregation that is important, but the optical density.
To understand the principle of operation of a refractometer, it is enough to remember that in the layer of the analyzed solution, absolutely the same refractive processes occur (hence the name - manual refractometer). There really is no other way to describe it. Well, for example, “a refracting ray of light” is too pretentious...
A carefully processed lens - in the picture, dark blue, like a boundless sea, is optically homogeneous, and its refractive index is unchanged. This is guaranteed by the manufacturing quality of the manufacturer.
If the density of the protective glass and the prism remains unchanged throughout its entire service life, then the only medium that can change the readings is the thinnest film of solution between the glass and the prism.
As the density of a solution droplet increases, evenly placed between the lens of the measuring device and protective glass, a line of light moves up or down on the Brix scale - a kind of display - and is visually observed through a monocular lens.
In other words, a refractometer is a measuring device that deflects a beam as the concentration of the liquid being tested increases (decreases). The principle of operation of a refractometer is based on this.
Note important function individual adjustment. Optics is limited not only to the phenomenon of refraction. A manual refractometer “takes into account” the visual acuity of the beholder - it only costs in a circular motion adjust the sharpness of the eyepiece and the readings will again become bright and clear.
Before mass production begins, marketers agree on the range of refractometers based on market expectations and customer needs. Engineers design a line of measuring instruments depending on the scope of application - first of all, they develop models for each niche depending on the expected concentration of the chemical compounds being analyzed.
The principle of operation of the refractometer remains unchanged, but the upper limit changes:
Based on them technological process, it is necessary to determine in advance the maximum upper limit and buy a refractometer for which the degree of saturation of the solution and the optical density of the medium under study will never reach the values when the beam deviates beyond the scale and the readings go off scale.
A refractometer is a unique direct-action measuring instrument. And there is no pathos here. There are only 3 theses:
The principle of operation of a refractometer is very simple - you can measure the content of a dissolved substance in a solution almost instantly - at the speed of light!
Remembering your school physics course and understanding how a refractometer works is important, but in order to profitably use all the possibilities and measure the concentration of a solution with a minimum error, you should remember!
Refractometry(from lat. refractus- refracted and Greek. metreo- measure) - a method of analysis based on the phenomenon of refraction of light when passing from one medium to another. The refraction of light, that is, the change in its original direction, is due to at different speeds distribution of light in various environments.
In this case, the ratio of the sine of the angle of incidence of the beam ( ε ) to the sine of the angle of refraction
(ε 1) for two contacting media there is a constant value called the refractive index (n).
Rice. 1. Ray path at the interface between two media
n = -------
Refractive index ( n) depends
From the nature of substances;
On temperature (the refractive index is determined at a temperature of 20 0 C);
From the concentration of the solution;
From the wavelength (measurements are made at a wavelength of 589.3 nm).
Note: When the substance concentration is less than 3- 4% it is not recommended to use the refractometry method.
Refractometer is a device used to determine the refractive index of light rays in transparent liquids. The principle of operation of the device is based on the phenomenon of total internal reflection, which occurs at the interface between two media, when a beam passes from an optically denser one to
optically less dense medium.
As a result, a sharp boundary between light and dark areas is formed in refracted rays.
The main part The refractometer is a system of two rectangular prisms (Fig. 2), made of glass with a high refractive index (n = 1.7). The limits for measuring refractive indices are 1.3-1.7.
The refractive index measured at 20°C and a light wavelength of 589.3 nm is designated by the index n 0. Refractive index n 0 for water measured under these conditions is equal to a constant value of 1.3333.
The dependence of the refractive index on the concentration of a substance in percent is expressed by the formula:
C % =-------
In g/ml with the following formula:
C g/ml =-------
where n and n 0 are the refractive indices of the solution and solvent; C is the concentration of the substance in solution; F is the refractive index factor.
The values of refractive indices and factors for various concentrations of solutions of substances are given in the refractometric tables, which are available in Appendix 4.
Refractometer device
Fig 3. Appearance refractometer IRF-454
The IRF-454 refractometer consists of the following main parts: body 2, telescope with eyepiece 1 and refractometric unit 3, the lower part is a measuring prism, and the upper part is a lighting prism.
The refractometric unit is rigidly connected to the scale of the reading device located inside the device body. To find the border
section and align it with the reticle crosshairs, it is necessary to tilt the refractometric unit to the desired position by rotating screw 8. For
A compensator serves to eliminate the coloration of the observed interface. Screw 10 can be used to rotate the compensator prisms simultaneously in different sides, while eliminating the colored border border
section. The liquid under study is illuminated by mirror 6 (in Fig. 3 it
shown in closed position), and the refractive index scale is
mirror 5.
Operating procedure
1. Before starting measurements, check the cleanliness of the contacting surfaces of the prisms.
2. Checking the zero point. Apply 2-3 drops of distilled water to the surface of the measuring prism and carefully cover with the lighting prism. Open the lighting window 3 and set it in the direction of the highest intensity of the light source using mirror 6. By rotating screw 8, obtain a sharp, clear, colorless distinction between the light and dark fields in the field of view of the eyepiece. Rotating screw 8, draw a line of light and shadow exactly until it coincides with the point of intersection of the line in the upper window of the eyepiece. The vertical line in the lower window of the eyepiece indicates the measurement result - the refractive index of water at 20°C is 1.333. In case of other readings of the refractive index of water, the measurement should be repeated, pre-treat the refractometric unit 3 with alcohol and wipe thoroughly with filter paper.
3. After installing the device to the zero point, lift the chamber of the lighting prism and wipe off the water with filter paper. Then 1-2 drops of the test solution are applied to the plane of the measuring prism, and the chamber is closed. Rotate the screws until the border of light and shadow coincides with the point of intersection of the lines. The refractive index of the solution is measured using a scale in the lower window of the eyepiece.
Refraction is a measurement using the refraction method. This term was coined in the 18th century by Newton. A refractometer gets its name from its operating principle. The principle of a refractometer is to measure the concentration of solutions and oils through the refractive index of light.
The refractometer device is based on a prism. Today there are several types of such devices:
Industrial and laboratory devices are used in factories and research centers. They are not portable because they are large. Heavy devices are usually not moved; they are used on site. The advantage of such equipment is the high accuracy of the indicators.
Digital and manual mechanical refractometers are highly mobile. They are small and light, such devices can be easily transported. The refractometer scale is displayed on a hand-held mechanical instrument. A digital refractometer displays the refractive index in numbers without a scale.
Industrial and laboratory refractometers have one important advantage - they are characterized by high accuracy of indicators. Such devices are used in laboratories of large enterprises. For example, a cutting fluid company tests oils using laboratory instruments. An automobile manufacturer can select oils and other fluids for vehicles using an industrial refractometer.
Manual mechanical and digital instruments are used where great importance has equipment mobility. For example, in a car service it is better to use one of the compact and simple devices. The TechLube RB-18 ATC handheld refractometer is ideal for such purposes. The refractometer scale will quite accurately display the concentration of coolant and other liquids (including antifreeze).
The TechLube RB-18 ATC refractometer does not have batteries, it is ideal even for field conditions. If you need to quickly measure the concentration of a substance, a refractometer will display the refractive index instantly. It is enough to apply a little substance to the lens. Even a beginner who has no experience in carrying out such measurements can cope with this task. You can master the measurement procedure in a few minutes.
An electronic refractometer has expanded functionality - this is the main advantage of a portable device. It can display the refractive index and density of the composition simultaneously on the LCD screen, converting the results into the desired units of measurement. The device is convenient, but requires more experience and requires batteries.
The design of a refractometer can be illustrated using the example of a simple and practical TechLube RB-18 ATC device. The main element of the device is a prism with a high refractive index. It is on this that the test substance is applied, the concentration of which must be determined.
A ray falls on the lens and is refracted at a certain angle. The angle of refraction of light in a lens on which a substance (for example, coolant) has already been applied depends on the density of the substance under study. The light, refracted, hits the lens system and is displayed on the scale. The refractive index is the relationship between the angle of entry of the beam and the angle of refraction in the medium.
The principle of a refractometer has been used for a very long time; the device is used in many fields. It has proven its effectiveness. The refractometer device has been improved over time, and digital instruments have appeared, but the system operates according to the old scheme.
The refractive index can change due to temperature. In some devices, the temperature of the substance is kept stable thanks to a special bimetallic plate. If the temperature of a substance rises or falls, the plate reacts to this. It adjusts the scale readings taking into account changes in the temperature of the substance. However, such a function is needed in some cases.
In order for the refractometer scale to show accurate results, it is necessary to prepare the instrument for use and carry out the calibration procedure. For such purposes, the most common distilled water is used. It is needed in order to set the value to zero. It is known that distilled water does not affect the refraction of light in the lens in any way - it gives a zero coefficient.
To prepare the device, apply a little distilled water to the main lens using a pipette. Then the device is closed and set to zero using the calibration screw. When the value 0.0 is set, you need to clean the lens with a special cloth. After such a little preparation, you can conduct research - the refractometer will display the refractive index very accurately.
You can set up the TechLube RB-18 ATC handheld refractometer in the manner described above. It is very easy to use. After calibration the device gives exact values. Using the device is not difficult - just repeat the same steps as during calibration, without touching only the calibration screw.
To carry out measurements, you need to apply a substance to the lens with a pipette, then you need to close the glass and wait about 30 seconds. When 30 seconds have passed, you can point the device at any available light source. It could be the sun or a light bulb - the power source will not affect the value. The refractometer will display the refractive index even in dim lighting.
The main thing is not to touch the calibration screw during the measurement process, otherwise you will have to carry out the entire procedure from scratch. When you have to carry out many measurements using different liquids, it is worth calibrating the device and cleaning it more often. Otherwise, errors in the indicators are possible.
An example of a simple but effective device is the TechLube RB-18 ATC. An optical refractometer is ideal for measuring the concentration of water-miscible cutting fluids. It has an automatic temperature compensation system, which sets it apart from many similar devices. If the temperature of the test composition changes, this will not affect the refractometer readings.
The device guarantees high accuracy measurements in any conditions. You can take the device with you on the road, use it in a laboratory, at an enterprise, in a car service center or in a garage. The refractometer will not take up much space.
The device is resistant to mechanical damage. To calibrate it, it is enough to have some distilled water. TECHLUBE offers discounts when purchasing refractometers in this series in bulk. The service life of such devices is long, they are reliable and practical. The durability of the device is ensured by its relatively simple design and high quality assemblies.
TechLube RB-18 ATC has a comfortable rubberized handle that does not slip in your hands. Even if your hands are covered in oil, the device will not slip out. The manufacturer has thought through the design of the refractometer down to the smallest detail, taking into account the specifics of its application.
Ophthalmology is moving forward by leaps and bounds. Over the course of several decades, laser surgery has managed to advance almost from zero to incredible heights, and almost all manual methods studies of the organ of vision were replaced by hardware ones. There is no need to explain that they are much more accurate and reliable than studies that require calculations and measurements from humans. But the eye is not only a sensory organ, but also a highly complex optical system that requires filigree precision. Eat diagnostic methods, which are rarely used, only in special cases. But there are, on the contrary, routine ones, without which eye examination is no longer possible. These include refractometry - what is it, how and why is it carried out, how should its results be interpreted?
Refractometry is the measurement of the refraction of the eye. However, one cannot talk about refraction without paying attention to how the eye is structured, at least in general terms.
Table. What does the organ of vision consist of?
| Anatomical unit | Characteristic |
|---|---|
| Auxiliary apparatus | Eyelids, eyelashes, eyebrows, eye socket, lacrimal glands and their system, muscle complex. |
| Eyeball | This is the perceptive apparatus of the organ. A light beam penetrates through its transparent elements and is fixed on the retina. In turn, it has several layers in its structure and plays a major role in the processes of refraction and accommodation. |
| Conducting system | Nerves connecting the retina and brain structures. |
| Subcortical elements and higher nerve centers | Areas in the brain responsible for processing visual signals. |
Separately, the structure of the eyeball should be considered. It consists of several structures:
Most people in their lives have come across or at least heard about such concepts as “myopia” and “farsightedness”. These words are not scientific terms and replace the more complex “” and “”, but they describe precisely violations of the refractory ability of the visual analyzer.
The process of refraction is the ability to bend light rays. The eye is a system of optical media, and the main refractive elements are the cornea and lens. All other transparent media are light-conducting. In order for the refraction and transmission of light to take place fully, all media must be perfectly transparent.
In ophthalmology, there is a concept of physical and clinical refraction. This is due to the fact that the eye is not only a set of light-processing structures, but also an organ of the nervous system.
Physical refraction‒ this is directly the ability of the eye to refract light beams; refractive power is described in diopters. Newborn children see practically nothing and the refractive power of their eyes does not exceed 50 diopters. But gradually the clarity of vision increases and eventually increases to 70 diopters.
And at this moment the game comes into play accommodation. This, in turn, is the process of changing the configuration of the lens, which is aimed at increasing image clarity - focusing. In ophthalmology, such concepts as the nearest and further point of clear vision are accepted. The further one is at infinity - at complete relaxation muscles responsible for accommodation. But as soon as a person needs to look at an object located closer to this further point, tension of the eye muscles becomes necessary.
In this regard, two types of clinical refraction are distinguished.
So, based on the above information, the definition of refractometry as the process of measuring refraction becomes more clear. Clinical refraction is examined, since the ability to focus images on the retina is important. Moreover, both the static and dynamic components are studied.
Some time ago, refraction could only be measured manually. For this purpose, special eye diagrams and manual refraction measurement techniques were used. In terms of accuracy, they were largely inferior modern devices Moreover, the possibility of error could not be ruled out.
Today, refractometry is a high-tech procedure that takes no more than five minutes. For this diagnostic method we use special devices- refractometers. The operating principle of this device is infrared radiation. The refractometer is located on the table, is about half a meter in height and has “outputs” on both sides - a screen with a control panel for the doctor and a special device where the patient looks. From a special lens, a beam of rays in the infrared spectrum is directed towards the pupils of the subject, which, penetrating through a hole in the iris, fall on the retina. There is a reflection from the bottom of the eye and return to the sensors of the device. The doctor only needs to direct the rays through the patient's pupil. The devices, in turn, record the received data, and the computer calculates the necessary indicators. The calculations are immediately displayed on the screen and can then be printed.
Despite the simplicity, fast execution and lack of any negative consequences procedure, it is irrational to carry it out to everyone. Typically, refractometers are used in specialized ophthalmological centers, where vision is checked before any surgical interventions and other serious procedures, and the technique is also used to clarify the degree of refractive error after the primary diagnosis of visual impairment by a doctor. The use of refractometry as one of the routine dispensary examinations is possible, but not every hospital can afford it.
Clear indications for refractometry:
Contraindications to this technique are very conditional. Of the highly specific ones, only one is a violation of the transparency of the vitreous body, or a disease such as cataracts. From non-specific:
In order for the results to be as reliable as possible, short preliminary preparation is necessary. It consists of instilling a solution of atropine into the eyes in the morning and evening for three days before the intended examination.
The dose of instilled atropine is 1 drop in each eye. Depending on age, the concentration of the solution may vary:
When preparing, you should be careful, since such drops in the eyes can cause transient blurred vision, which is especially dangerous for drivers and people whose activities require maximum eye strain and attention to detail. In addition, atropine is a fairly strong allergen, so allergic conjunctivitis may develop - redness, tearing.
The actual process of performing refractometry is simple.
With hardware refractometry, several types of indicators can be detected on a printed sheet separately for the right (R) and left (L) eyes.
There is no need to be able to decipher these values yourself: the doctor will inform you about any deviations. But it is recommended to save the data after the study so that monitoring can be carried out over time.
The main point of the conclusion voiced by the doctor is the type of refraction and the degree of visual impairment (important for obtaining lenses or glasses). Types of refraction:
Thus, refractometry is a modern informative method for diagnosing the state of vision, which takes a minimum of time, is absolutely safe for both adults and children, and is also very easy to perform.
Having chosen beekeeping as a hobby or as the main activity, you need to understand all the instruments and technical devices that help you obtain high-quality, tasty honey. You definitely need to know about a honey refractometer: what is it and how to use it?
At least the requirements modern market the quality of products is not high, many beekeepers still rely on the proven GOST. According to it, the mass fraction of moisture content in honey should not exceed 19-21%.
To obtain such results, it is believed that it is advisable to pump out honey only from those combs that have been covered with wax to three-quarters of the total height. But when pumping out honey, this requirement is not always met, as a result of which the water content in the collected product significantly exceeds the norm.
Honey high humidity is a favorable environment for fermentation processes, which quickly make it unfit for consumption. To avoid such situations, during the collection process you need to strictly control the water content; for this you will need a honey refractometer. It accurately measures the mass fraction of water in the total mass of the product. This device has long been used not only by beekeepers, but also by wholesale honey buyers.
In general, refractometers are designed to test sugar-containing liquids such as fruit juices and drinks, wines and honey. When choosing a device specifically for honey, you need to pay attention to some parameters:
Portable devices are very compact and do not require connection to a power supply. More technologically advanced models are equipped with a built-in temperature corrector, which is a bimetallic plate connected to the optics system of the refractometer itself.
Under the influence of temperature fluctuations, this plate is compressed or, conversely, stretched, thereby smoothly adjusting the operation of the entire measuring system in accordance with temperature conditions. Thanks to automatic calculations of these shifts, maximum accuracy is achieved when measuring humidity in the range from 12% to 27%.
Before purchasing the device, you should carefully read the instructions. Before the first use, it is necessary to calibrate the refractometer. It must be carried out according to the readings of a reference device, using identical honey samples. To make adjustments, you need to clean the calibration screw with a screwdriver and enter the border, which is most often painted blue and white, to read the same as the standard.
Video: refractometer for honey.
Having understood what a refractometer is and how it works, it becomes clear that for maximum accuracy measurement results, the device must be carefully calibrated. It is also possible to draw conclusions about the influence on the temperature measurements taken not only of the product, but also environment. Moreover, the measuring prism itself must also be at room temperature.
There are no special requirements for storing the refractometer. It should be cleaned with a soft damp cloth after the last measurements and placed in dry room so that the measuring eyepiece does not fade. You should not try to disassemble the device and clean it yourself; it is better to contact a specialized service center.
