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 highly accurate. 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 it needs 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.
It is also used during vision correction with glasses or contact lenses.
The device is a complete system for converting and recording infrared radiation. Based on indicators of reflected radiation such as intensity and wavelength, a special program of the device carries out calculations. The decoding results will indicate the refraction (refractive power) of the optical media of the eye.
To understand why research is used in ophthalmology, you should know the structure and basic principles of operation of a refractometer.
They are based on these key points:
There are several medical indications for conducting research using a special automatic analyzer:
Also, research using a refractometer is necessary when conservative methods vision correction. An examination on the device is mandatory when wearing it in order to monitor the progress of treatment.
Refractometry is an outpatient procedure that is performed in a specially equipped office. The examination is carried out in a non-contact manner, therefore it does not require medical personnel preliminary preparation in compliance with the rules of asepsis and antiseptics.
To obtain a reliable result, as well as to eliminate errors, the pupil is first dilated using the drug atropine. It belongs to the pharmacological group of M-anticholinergic drugs and leads to temporary paralysis of the eye muscles that constrict the pupil.
Atropine in the form of eye drops is prescribed 3 days before the intended examination. Eye drops are instilled 2 times a day at approximately equal intervals (morning and evening).
During the procedure, the patient sits on a chair in front of the device, and rests his head against a special stop. The doctor asks you to focus your gaze on the sensors and not move.
After the device starts operating, the sensors emit infrared radiation, which is reflected from the retina of the eye, passes back and is recorded. The duration of the study using an automatic refractometer does not exceed two minutes for each eye.
After conducting the examination using an automatic device, it issues a printout that displays the main indicators in the form of letter values and numbers.
They have the following decoding:
The number of indicators depends on the specific model of ophthalmic automatic refractometer that was used for the examination.
The examination, which is carried out using a refractometric device, helps to avoid medical errors and accurately establish the diagnosis. This saves time for the doctor and the patient. And thanks to the non-contact nature of refractometry, it also eliminates physical discomfort for the patient.
List of sources:
So, what kind of beast is this refractometer? And what do you eat it with?
The review is a logical continuation of the topic about and belongs to the category “but men don’t know!” :)))
Well, let's get started:
First, a lyrical digression. As you already know, my friends, I am the proud owner of a Chinese moonshine still. It came with a set of three alcohol meters along with a thermometer. And everything would be fine, and everything would be wonderful, if not for one BUT. To measure the percentage of alcohol in a liquid, a decent amount of this very liquid is needed. According to the instructions, it comes out to 300 grams! This is the most important inconvenience. You can no longer measure the degree in a glass.
“Is there such a device,” I asked myself, “that can show the percentage of alcohol using a minimum amount of liquid?” He asked and began to search. It turned out that there is such a device! Almost immediately I came across a device with such a mysterious name - “refractometer”. And my eyes were opened, and I saw that this was good :)
With this miracle device you can measure the percentage of alcohol in a liquid using just two or three drops of it! Refractometers, as it turned out, are a great many. Refractometers for beer, wine, honey, milk, antifreeze, electrolyte, aquarium, etc. But, nevertheless, the principle of operation is the same for everyone. They differ only in their scale and the ability to automatically correct the result depending on the temperature. From 0 to 30 degrees. This is just such a function. There is an ATC sticker and it costs more than a device without temperature correction. It also has a calibration screw, closed with a rubber plug and a screwdriver included.
Now let's turn to Wiki:
“A refractometer is a device that measures the refractive index of light in a medium.
Refractometry is a method for studying substances based on determining the index (coefficient) of refraction (refraction) and some of its functions. Refractometry (refractometric method) is used to identify chemical compounds, quantitative and structural analysis, determination of physical and chemical parameters of substances. The refractive index n is the ratio of the speed of light in the adjacent media."
Oh how! Neither more nor less, but we are pulling the speed of light itself by the tail! Cool :)))
Once again I am convinced that after drinking moonshine, you can’t pull anyone’s tail! ha ha ha!!!
So how does it work. We take a refractometer. We look through the hole into the light. We focus on the scale. Open the top glass. We put moonshine (vodka, tequila, etc.) into a pipette, drop two or three drops onto the bottom glass and close the whole thing with a clamp with the top glass. Again we look through the hole into the light. Let's smile :)
The scale with uneven graduations looks exactly the same as on the seller’s website. That is, like this. 
The only caveat. The scale in the picture says ALCOHOL. Mine says ALCOHOLIC. A subtle hint though...
Here's what the complete set looks like. 
Refractometer
Pipette
Screwdriver
Napkin
Instructions
Case
Other photos
Neat box-case 
Everything is packed compactly 
Calibration screw 
Open glass 
Eyepiece 
In hand 
I'm planning to buy +54 Add to favorites I liked the review +59 +121
Concentration measurement process various substances The method of measuring refraction and determining the refractive index got its name - refractometry. Devices that use the principle of refractometry in their work are called refractometers. Refractometers are widely used in various industries: for identifying chemical compounds, determining physicochemical parameters, for quantitative and structural analysis. IN Food Industry- for measuring the alcohol content in alcoholic products, monitoring the sugar content in sugar production- in general, to establish quality food products. In pharmacology, refractometers are used to determine the amount of glucose in biological fluids and drugs in solutions. Advantages of refractometric methods of chemical quantitative analysis- fast measurements, low consumption of substances and high accuracy.
Objective of the work: Refractometric method as a method for analyzing medicinal substances. The relevance of using ATAGO refractometers and polarimeters in pharmaceuticals and, in particular, in pharmacies.
The refractive index (refractive index) is the ratio of the speed of light in a vacuum to the speed of light in the test substance (absolute refractive index). The refractive index depends on the temperature and wavelength of light at which the determination is made. In solutions, the refractive index also depends on the concentration of the substance and the nature of the solvent. In this case, in practice, the so-called relative refractive index (n) is determined, which is calculated as the ratio of the sine of the angle of incidence of the beam (α) to the sine of the angle of refraction (β) for two contacting media.
The refractive index is also equal to the ratio of the speeds of light propagation in these media:
In laboratory conditions, the so-called relative refractive index (RI) of a substance with respect to air is usually determined. PP is measured using refractometers various systems. Previously, RI measurements were most often carried out using Abbe refractometers, which operate on the principle of total internal reflection when light passes through the interface between two media with different refractive indices. Nowadays, in the laboratory you can increasingly find automatic refractometers ATAGO RX series.
The range of measured RIs when measured in transmitted light using Abbe refractometers is 1.3000 – 1.7000. If it is necessary to push the boundaries of the ranges, special models with low or high ranges, as well as multi-wavelength Abbe refractometers, are used.
The range of measured PPs when measured on automatic refractometers of the RX series is 1.32500 – 1.70000. The accuracy of refractive index measurement must be no lower than ±2·10-4. The value of the refractive index depends on the nature of the substance, the wavelength of the light, the temperature at which the measurement is made, and the concentration of the substance in the solution. Typically, refractive index measurements are made at a light wavelength of 589.3 nm (line D of the sodium spectrum). But in some cases, different wavelengths are used in the range from 450nm to 1550nm. Very an important condition definition of PP is compliance temperature regime. Typically, determination is performed at 20 degrees Celsius. At temperatures above 20 degrees, the PP value decreases; at temperatures below 20 degrees, the PP value increases.
Temperature correction is calculated using the formula: n1=n20+(20-T)*0.0002
The refractive index measured at 20°C and a light wavelength of 589.3 nm is designated n20. The refractive index can be used as a constant to determine the authenticity and purity of those medicines, which are liquids in nature. The refractometric method is widely used in pharmaceutical analysis to quantify the concentration of substances in a solution, which is found from a graph of the refractive index of a solution versus concentration. On the graph, select the concentration interval in which it is observed linear dependence between refractive index and concentration. This method can be used in the practice of intrapharmacy control.
The dependence of the refractive index on the concentration of a substance in percent is expressed by the formula:
where n and n0 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 refractive index of a solution is the sum of the refractive index of the solvent and the refractive index of the dissolved substances.
The values of refractive indices and factors for various concentrations of solutions of medicinal substances are given in refractometric tables, which are available in the manual for intrapharmacy control. Using tables greatly simplifies calculations.
Dependence of the refractive index of aqueous solutions of some substances on concentration: In refractometry, two methods are used to calculate the concentration of a substance in a solution based on the measured refractive index.
The value of the refractive index factor is taken from refractometric tables.
Having measured the refractive index, the corresponding concentration value is found in the table. If the measured refractive index is not given in the table, interpolation is carried out. The refractometric method is used for the quantitative determination of concentrated solutions. Concentrated solutions are working solutions of medicinal substances (DS) of a certain, higher concentration than these solutions are prescribed in pharmacies.
When preparing concentrated solutions, concentrations close to saturated should be avoided, because When the temperature of the solution decreases, crystallization of the dissolved substance is possible.
Deviations allowed in concentrates:
1) The concentration of the solution turned out to be higher than required.
The volume of water required to dilute the resulting solution is calculated using the formula:
where X is the amount of water required to dilute the prepared solution (ml.); A is the volume of the prepared solution (ml); B - required solution concentration (%); C is the actual concentration of the solution (%).
2) The concentration of the solution turned out to be lower than required.
The mass of the drug to strengthen the resulting solution is calculated using the formula:
where X is the mass of the substance that should be added to the solution (g); A is the volume of the prepared solution (ml); B - required solution concentration (%); C is the actual concentration of the solution (%); ρ20 - solution density at 20°C (g/ml, g/cm3)
NAR-1T Liquid 
DR-A1 The NAR or DR-A1 series refractometers are designed to measure the refractive index and average dispersion of non-aggressive liquids. These are very high quality devices. Easy to maintain. Minimal in content. Actually consumables for these refractometers - a light bulb (light source). ATAGO refractometers of the NAR or DR-A1 series are used:
To determine the proportion of dry substances in various worts (GOST 5900-73), sugar agar syrup, syrup for marmalade, marshmallows, creams and gingerbreads.
To determine the mass fraction of soluble solids by sucrose (% Brix) in processed fruits and vegetables, to determine the percentage of fat in solid foods (gingerbreads, waffles or baked goods) and salt concentrations.
4. When servicing equipment, ATAGO refractometers are used to determine with greater accuracy the volumetric concentration of anti-crystallization liquid "IM", which is added to aviation fuel in an amount of 0.1 to 0.3%. Further processing of the results is carried out according to " Methodological recommendations on analysis of the quality of fuels and lubricants in civil aviation" Part II p. 159. Experience in the use of refractometers has shown that these devices significantly reduce the time and increase the reliability of obtaining analyzes on the percentage of liquid "IM" in aviation fuel.
Automatic refractometers Auto laboratory refractometers The microprocessor-controlled RX series are designed to test the concentration of a wide range of liquid media of both low and high viscosity, regardless of clarity and color. The RX series provide high measurement accuracy, precise temperature control. The entire measurement process (heating/cooling) takes place automatically. Simply press the Start key. The device automatically measures the refractive index of a solution sample, calculates its concentration and displays the result on a digital LCD screen. The RX-I series is equipped with a screen that is made using Touch Screen technology - a touch screen, all control of the device is carried out from the screen. Automatic refractometers of the RX series can both heat/cool the sample using built-in Peltier elements, and use the automatic temperature compensation function when performing measurements. The ideal instrument for pharmacists in this series is the RX-9000-i and RX-5000-i Plus automatic refractometer.
Ethyl alcohol (ethanol, Spiritus aethylicus) is one of the most widely used organic solvents in medical and pharmaceutical practice. Ethanol has bacteriostatic and bactericidal properties. Widely used to obtain tinctures, extracts, dosage forms for external use. The quality of alcohol solutions depends on the concentration of alcohol in which the drug is dissolved. In each case, an optimal concentration is required at which the drug substance does not precipitate. Therefore, water-alcohol solutions with different alcohol concentrations are prepared. The quantitative content of ethyl alcohol is easily determined by the refractometric method. There is a clear relationship between the concentration of ethyl alcohol and the refractive index. It is known that the refractive index depends on temperature, wavelength of light, the nature of the substance and solvent, and the concentration of the substance. So, the refractive index of aqueous alcohol solutions from 1% to 70% has a linear characteristic, which means you can easily measure the concentration with a refractometer. ATAGO produces special refractometers for measuring alcohol concentration. In general, these are ordinary refractometers, but a special correction factor is built into the processor, which allows you to immediately display the concentration of an aqueous-alcohol solution on the display, bypassing the refractive index. At concentrations from 70% to 96%, the dependence is nonlinear. Thus, the refractometric method can determine the strength of alcohol in the range from 1% to 70%.
Let's consider the use of refractometers in the manufacture and analysis of a 10% glycerin solution for injection: Glycerin solution 10% Glycerin (in terms of anhydrous) 100 g
1. Sodium chloride 9.0 g. Water up to 1 liter.
Manufacturing. Glycerin (highest grade, dynamite) with a quantitative content of 86-90%, 94-98% or more is purchased from suppliers. Therefore, in order to calculate the amount of initial glycerin, it is necessary to know exactly what the mass fraction of anhydrous substance is in it. A refractometer is used to accurately measure glycerol concentration. The refractive index of the original glycerol n=1.4569 corresponds to a mass fraction of anhydrous substance of 89%. The initial amount of glycerin required to make the solution, according to the recipe, is 68:
2. Mass of glycerin = 100 g / 0.89 = 112.36 g.
Quantitative determination of glycerol in solution. We calculate the concentration of glycerol: Sglitz = /Fglitz
where n is the refractive index of the solution; n0 is the refractive index of purified water, measured at the same temperature; СNaCl is the concentration of sodium chloride in solution, determined by argentometry; FNaCl is the refractive index factor of the sodium chloride solution for the found concentration; Fglyc is the refractive factor of a 10% glycerol solution (0.001156).
IN pharmaceutical industry ATAGO refractometers can be used to study aqueous solutions of various drugs: calcium chloride (0% and 20%); novocaine (0.5%, 1%, 2%, 10%, 20%, 40%); ephedrine (5%); glucose (5%, 25%, 40%); magnesium sulfate (25%); sodium chloride (10%); cordiamine, etc.
If for one of the substances included in the solution the refractive index factor is unknown or its insignificant concentration does not allow obtaining accurate data, then prepare a control solution containing this substance in the concentration that was determined by the titrometric method.
Refractometers and polarimeters from the Japanese company ATAGO have found application in all industries of the Russian Federation. ATAGO refractometers and polarimeters are included in the state register of measuring instruments of the Russian Federation. This allows the use of ATAGO devices in the most tightly controlled areas of production - such as, for example, pharmaceuticals.
