Immersion Oil: Description, Application and Feedback

The immersion method of microscopic observation presupposes the introduction of a special liquid between the objective of the instrument and the object under study. It provides increased brightness and wider image enlargement boundaries. Thus, the object can be greatly approximated and considered the smallest of its elements, without changing the equipment. Accordingly, the liquid is called immersion. As it can act a variety of compositions. . The most popular is immersion oil . Let's consider its features in more detail.

General information

The first immersion oil for microscopy was cedar. However, it had one significant drawback. Over time, its properties changed, and it did not allow to obtain the desired results. In the open air, the liquid began to compact gradually (until hardening). Accordingly, the index of refraction also changed . . In the 20th century, synthetic immersion oil was produced. This liquid had no such drawback.

Immersion Oil: Standards

The key fluid parameters are set in GOST 13739-78. обладает: According to the standard, immersion oil has:

• Refractive index nd = 1,515 ± 0,001;
• Transmittance in the spectral range from 500 to 700 nm with a layer thickness of 1 mm - 95%, from 400 to 480 nm - 92%;

, считается 20 градусов. The optimum temperature at which immersion oil can be used is 20 degrees. There are also international standards. According to ISO 8036/1, the refractive index is 1.518 + 0.0005, and the transmittance at the layer of 10 mm for the spectral range from 500 to 760 nm is 95%, and at 400 nm - 60%.

. The indicated parameters correspond to immersion non-fluorescent oil . In the standard ISO 8036-1 / 2, the fluorescence liquid for the luminescence is determined. The transmittance at the spectral range from 500 to 700 nm in the 10 mm layer is 95%, from 365 to 400 nm - 60%.

Differences in the parameters

The difference found in the above standards may lead to a deterioration in the performance of a particular lens when using an inappropriate liquid. As a result:

1. Reduces the contrast due to the appearance of spherical aberration.
2. The field is painted on the object of investigation.
3. Illumination in the plane of the studied object and in the area of formation of its image becomes uneven.
4. The picture becomes unsharp.

Nuances

Optical microscopes have an upper limit of resolution slightly higher than 100 times. At this level of magnification, the illumination of the object under study must be qualitative. Otherwise, the resulting image will be so dark that it will be impossible to view the object. The fact is that refraction and diffusion of light occurs between the cover glass and the lens. Immersion oil promotes more capture. As a result, the image becomes clearer.

Features of light refraction

How to get a clear picture? In different environments, the refraction of light occurs in different ways. For example, the refraction angles of the rays in air and glass differ. In the first case, the indicator is 1.0, in the second case - 1.5. This is the main problem.

The use of oil makes it possible to reduce the refractive index of the rays that pass through the object under study. The fact is that the liquid has the same parameter as the glass. As a result, a homogeneous medium is formed between the slide and the lens, and most of the light passing through the object enters the instrument. This results in a clear image.

Technical issues

As a rule, on the cases of lenses intended for immersion, there is engraving Oil. The same element is used when an aperture of 1.0 or more is needed. These "immersion" lenses are used for direct immersion in a liquid. In this connection, they are completely hermetic. This provides high protection against lens damage by oil.

Classification

In practice, two viscosities are used: high (type B) and low (A). Often on the packaging you can find information about the refractive index. оэффициент преломления которого равен 1.515. For example, let out oil immersion (100 ml) , to which refractive index is equal 1.515. Liquids with low viscosity are applied to airspace, and with high - together with condensers.

Terms of Use

To get a clear image of the object under study, follow simple enough recommendations:

1. Find the studied object on the slider in the center of the field on a small magnification. For this purpose, a lens of small multiplicity is used.
2. Rotate the turret.
3. Enter the lens 100 times in the working position.
4. Place a drop of oil on the slide glass, the second on the lens.
5. Adjust the working distance with fine focus until a clear picture of the subject appears.

Care must be taken during operation. It is important not to let air in between the cover glass and the lens.

Oil immersion "Minimed"

The liquid is used when working with achromatic and apochromatic lenses of any type of instrument, except for fluorescent ones. As noted by experts who used this immersion oil, it has several useful properties. The liquid significantly improves the visibility of the object, minimizes glare, loss of light and optical aberration. The use of oil greatly extends the range of equipment possibilities.

Cleaning of equipment

After working with immersion oil, it is necessary to put the device in order. Cleaning should be done before the lens dries. Use clean lens paper to remove residual oil. All glass surfaces are cleaned with a rolled sheet. Lens paper should be moistened with a special solution and remove any residual oil.

Historical reference

The first scientist who explained the mechanism of immersion was Robert Hooke. In 1678, his book Microscopium was published, in which all explanations were given. In 1812, immersion was proposed as a means of correcting lens aberrations. The author of the idea was David Büster. Approximately in 1840, the first immersion lenses were manufactured. Their creator was D.B. Amichi. Initially, as an immersion fluid, researchers used anise oil. The refractive index was close to that of glass.